Celestial Warrior

1 00:00:00,050 --> 00:00:06,420 Hey, in this lecture you'll learn about loops and loops are very important. 3 00:00:06,420 --> 00:00:10,590 They are one of the fundamental building blocks of the Python programming language 5 00:00:10,590 --> 00:00:15,809 and of every other programming language as well because loops are crucial. 7 00:00:15,809 --> 00:00:21,630 So what are loops? Well loops are basically the way that allows you to execute the 9 00:00:21,630 --> 00:00:26,789 statement multiple times, so what does that mean? Let's say you have a bunch of 11 00:00:26,789 --> 00:00:32,040 files, text files and you want to insert a certain string inside each of these 13 00:00:32,040 --> 00:00:37,140 text files, so you'd have to open those text files in Python by writing the 15 00:00:37,140 --> 00:00:42,090 Python code that corresponds to opening a file and then you insert that string 17 00:00:42,090 --> 00:00:46,649 inside the file and close the file and save it, so there is some code that does 19 00:00:46,649 --> 00:00:52,199 this opening and inserting the text and closing the file and if you had 100 21 00:00:52,199 --> 00:00:57,570 files you'd have to execute that code 100 times so you'd come up with let's 23 00:00:57,570 --> 00:01:03,480 say 100 lines of code but that doesn't sound very efficient so that's what loops 25 00:01:03,480 --> 00:01:08,970 are for. So a productive way to solve the problem that I just mentioned would be 27 00:01:08,970 --> 00:01:13,530 to create a list of these files so Python lists all of the file names and 29 00:01:13,530 --> 00:01:20,310 then you would use a loop to iterate through this list of file names and a loop 31 00:01:20,310 --> 00:01:25,439 would do all that in just a few lines of code and there are two kinds of loops in 33 00:01:25,439 --> 00:01:30,240 Python, there is a for loop and a problem for example that I just mentioned would 35 00:01:30,240 --> 00:01:36,600 be solved using a for loop and we also have the while loop. A while loop does 37 00:01:36,600 --> 00:01:41,700 also repeatedly execute a statement that you give, that you write and it 39 00:01:41,700 --> 00:01:47,280 executes it as long as the given conditional true, so let's say you have a user that 41 00:01:47,280 --> 00:01:52,770 is trying to login in your web app and while he keeps entering their own 43 00:01:52,770 --> 00:01:59,130 password, you'd continue executing a statement that would reject his login to 45 00:01:59,130 --> 00:02:04,049 your system, so while the password is wrong reject the user, something like that. 47 00:02:04,049 --> 00:02:09,149 So that's about the definition of the for loop and the while loop. In our 49 00:02:09,149 --> 00:02:14,370 next lecture I'll show you the syntax of the for loop and by also looking at an example, 51 00:02:14,370 --> 00:02:18,329 so see you in the next lecture.

In one of the previous exercises we created the following function: def string_length(mystring): return len(mystring) Calling the function with a string as the value for the argument mystringwill return the length of that string. However, if an integer is passed as an argument value: string_length(10) that wouldgenerate an error since the len() function doesn't work for integers. Your duty is to modify the function so that if an integer is passed as an input, the function should output a message like "Sorry integers don't have length". def string_length(mystring): if type(mystring) == int: return "Sorry, integers don't have length" else: return len(mystring) The function that we implemented in the previous exercise checks integer datatypes, but not about floats. So, please expand the conditional block so that floats are counted too. def string_length(mystring): if type(mystring) == int: return "Sorry, integers don't have length" elif type(mystring) == float: return "Sorry, floats don't have length" else: return len(mystring) In one of the previous exercisesyou created a function that convertedCelsius degrees to Fahrenheit: def cel_to_fahr(c): f = c * 9/5 + 32 return f Now, the lowest possibletemperature that physicalmatter can reach is -273.15C.With that in mind, please improve the function by making itprint out a message in case a number lower than -273.15 is passed as input when calling the function. def c_to_f(c): if c< -273.15: return "That temperature doesn't make sense!" else: f=c*9/5+32 return f print(c_to_f(-273.4))

1 00:00:00,620 --> 00:00:05,720 Hey, hello again. In this lecture you're going to learn about conditionals. What is a conditional? 3 00:00:07,980 --> 00:00:14,190 Well a conditional is a block of code which performs different actions depending on 5 00:00:14,190 --> 00:00:19,980 whether a given conditional evaluates to true or false so let's go ahead and 7 00:00:19,980 --> 00:00:29,340 create a conditional in Python. I'll create the file conditionals dot py and let me 9 00:00:29,340 --> 00:00:35,280 create a conditional block, and first of all let me create a variable. Let's say a 11 00:00:35,280 --> 00:00:40,920 equals five and here I'll create a conditional block. This block, what this 13 00:00:40,920 --> 00:00:48,780 will do is it will perform an action if a is less than five and another action 15 00:00:48,780 --> 00:00:54,930 if a is equal or greater than five so let me create that. If this, our 17 00:00:54,930 --> 00:01:04,049 conditional starts if a and let's say less than five print, let's say less than 5. 19 00:01:04,049 --> 00:01:15,030 Press ENTER and if you want to perform more actions with this conditional, with 21 00:01:15,030 --> 00:01:19,979 this condition so when this condition is true this will be executed but if you 23 00:01:19,979 --> 00:01:25,049 want to perform more actions you can add one there, if not then you can go to the 25 00:01:25,049 --> 00:01:32,159 next check. So that would be else, so you have a 27 00:01:32,159 --> 00:01:45,060 column here, a column there, so else print equal or greater than 5. Now let me 29 00:01:45,060 --> 00:01:53,520 execute it. And we get equal or greater than 5. So why did you get that? Well 31 00:01:53,520 --> 00:01:59,729 because you know if a is less than 5 which is not, so this evaluates to false, 33 00:01:59,729 --> 00:02:05,340 that means with this this will not be executed so Python will skip this line 35 00:02:05,340 --> 00:02:12,870 and it will go to the next one. This next line says else, so else means if this 37 00:02:12,870 --> 00:02:18,450 is not true, this will be executed, so equal or 39 00:02:18,450 --> 00:02:25,769 greater than five, so in this case if a is not less than five then there's no 41 00:02:25,769 --> 00:02:32,549 other option but a is either equal or greater than five, so that's an if and else 43 00:02:32,549 --> 00:02:36,959 conditional block. However if you want to add more conditions there 45 00:02:36,959 --> 00:02:45,569 you want to use elif, so let's do that the first two lines stay the same. If a 47 00:02:45,569 --> 00:02:57,840 is less than five print less than five elif a is equal to five print equal to 49 00:02:57,840 --> 00:03:19,019 five else print greater than five. Save and execute and you get equal to five. 51 00:03:19,019 --> 00:03:21,769 If a was six, you'd get greater than five and if a was 53 00:03:25,500 --> 00:03:34,500 three you'd get less than five. That's a conditional block in Python and 55 00:03:34,500 --> 00:03:39,480 yeah, try to get familiar with the syntax and in the next lecture I'm going to 57 00:03:39,480 --> 00:03:47,569 incorporate a conditional with this block of code, so see you there.

The next lecture will be an exercise and there will be more exercises as you progress through the course. The exercises are difficult and sometimes tricky and I don't expect students to solve them all. Most students actually fail to solve the exercisesunless they are already familiar with Python. The whole point of exercises is to force you to think about how to solve a problem independently. The next lecture following each exercise contains the solution where you can compare your approach. Create a functionthat converts Celsius degrees toFahrenheit. The formula to convert Celsius to Fahrenheit isF= C 9/5 + 32. In the previous exercises you used the interactive Udemy interface to write your code.For this exercise, please use your computertools (Python, editor, terminal,etc.). This will help you get used with Python in a real environment. Once you are done check your solution against my solution which islocatedin the next lecture. Don't worry if your solution is not exactly the same as mine. As far as the solutions generate the same output, your solution is most likely correct. def cel_to_fahr(c): f = c * 9/5 + 32 return f And here is an example of calling the function: print(cel_to_fahr(10)) That would return 50.0 which means 10 degreeCelsius is equal to 50 degreeFahrenheit. Create a function that takes any string as argument and returns the length of that string. def string_length(mystring): return len(mystring) And here's an example of calling the function: print(string_length("Hello")) That would return 5.

Tip: Note that not all functions have one input parameter. There are also simplerfunctions without any parameters at all. Example: def say_hello(): return "Hello" And there are also functions with more than one parameter but you will learn that in the next video.

1 00:00:00,500 --> 00:00:06,120 Hi again, in this video you'll learn how to create a function in Python and how 3 00:00:06,120 --> 00:00:13,380 to use that function, so let me go ahead and create a script. Let me name this my 5 00:00:13,380 --> 00:00:23,730 function.py and let's go ahead and create a function. Creating a function 7 00:00:23,730 --> 00:00:30,210 will always begin with the DEF keyword which is, which means define. Now that is 9 00:00:30,210 --> 00:00:33,980 followed by the name of the function, so you need to give your function a name 11 00:00:33,980 --> 00:00:43,350 let me name this minutes to hours and as you may guess already what I'm 13 00:00:43,350 --> 00:00:50,910 creating is a function that will convert minutes to hours, so you create the 15 00:00:50,910 --> 00:00:56,940 procedure on how to convert minutes to hours and then you can call that 17 00:00:56,940 --> 00:01:02,129 procedure, so you can call that function. You can give that function any values 19 00:01:02,129 --> 00:01:07,380 when you call it and the function will produce an output depending on the value 21 00:01:07,380 --> 00:01:12,659 and depending on the formula, on the procedures that you write in here, so 23 00:01:12,659 --> 00:01:16,860 let's go ahead and do that, minutes to hours. Now functions normally they have 25 00:01:16,860 --> 00:01:23,549 some input and they produce some output. The input goes inside these brackets 27 00:01:23,549 --> 00:01:29,130 here. In our case the input could be minutes so this is just a variable, you 29 00:01:29,130 --> 00:01:32,430 can give it any name that you want, you can give it any name that you want for 31 00:01:32,430 --> 00:01:38,939 the function name as well, so the input is minutes and then the output will be 33 00:01:38,939 --> 00:01:43,610 hours, but you don't write the output here. Here what to do you always choose a 35 00:01:43,610 --> 00:01:52,340 column, press enter and that will be auto indented, so as you see the functions 37 00:01:52,340 --> 00:01:56,969 everything that you write below the first line of a function definition is 39 00:01:56,969 --> 00:02:02,850 indented and every line after that, so the DEF keyword, the name of function, the 41 00:02:02,850 --> 00:02:09,720 input and here we write the body of the function. What we want to do is let's 43 00:02:09,720 --> 00:02:18,850 say variable house equals to minutes / 60 that should give us the 45 00:02:18,850 --> 00:02:26,290 hours. Note that if you are on Python 2 you want to do 60 point zero because 47 00:02:26,290 --> 00:02:31,540 if you do that you get an integer as an output, not a float, so in 49 00:02:31,540 --> 00:02:37,030 Python 2 you have to explicitly pass a float when you do division to get a 51 00:02:37,030 --> 00:02:42,190 number, to get a float with decimal point. I am in Python 3, so I don't 53 00:02:42,190 --> 00:02:48,340 need to put 60.0 there. And yeah, this is a simple function, so this is what the 55 00:02:48,340 --> 00:02:52,450 function will perform and then the last line of the function is normally a 57 00:02:52,450 --> 00:02:59,790 return keyword, so notice that these are reserved keywords def and return, and 59 00:02:59,790 --> 00:03:06,430 what I want to return is, well gets what? The output which is hours, so that's the 61 00:03:06,430 --> 00:03:11,769 idea, we are getting minutes. The user will input a value for that later when 63 00:03:11,769 --> 00:03:17,230 you call a function and Then minutes will be divided by 60 and that operation, 65 00:03:17,230 --> 00:03:22,810 that number will be stored in the hours variable which is a variable that exists 67 00:03:22,810 --> 00:03:27,700 only inside the function so this is called a local variable. If you call it 69 00:03:27,700 --> 00:03:32,470 outside the function it will not work, but we'll cover that later. And so then 71 00:03:32,470 --> 00:03:41,130 we return the value of that variable. Now I'll save this and open the terminal. 73 00:03:45,359 --> 00:03:58,329 Make some space there and let me execute the script. You get nothing and the 75 00:03:58,329 --> 00:04:04,390 reason for that is because what you did here is you just define a blueprint, you 77 00:04:04,390 --> 00:04:10,450 are not using the blueprint, so what you do next is you need to go ahead and use 79 00:04:10,450 --> 00:04:17,530 that blueprint, so which means you need to call that function, so backspace 81 00:04:17,530 --> 00:04:24,550 to go here to unindent. Indenting means that you are done with the 83 00:04:24,550 --> 00:04:27,700 function definition so when you start a new line, 85 00:04:27,700 --> 00:04:32,680 right here that means you are not writing inside function and so to call a 87 00:04:32,680 --> 00:04:37,840 function what you do is you just call the name of the function, minutes to hours 89 00:04:37,840 --> 00:04:44,920 and then you open brackets, then inside brackets you pass a value that you want 91 00:04:44,920 --> 00:04:51,400 to use as input, so let's say you want 70 minutes, you want to convert them to 93 00:04:51,400 --> 00:04:58,510 hours, save the script go and execute again you don't get any output, but let's see. 95 00:04:58,510 --> 00:05:02,770 As I said you won't get any output, so why is that? 97 00:05:02,770 --> 00:05:07,630 Well that's because you didn't perform a print operation there, you didn't call a 99 00:05:07,630 --> 00:05:16,780 print function so what you do is you print so open brackets close brackets 101 00:05:16,780 --> 00:05:22,630 and inside brackets give the function code, save your script, go here, execute 103 00:05:22,630 --> 00:05:28,900 and yeah you get the hours, so the minutes is equal to one point one six 105 00:05:28,900 --> 00:05:37,060 six six hours so it's important to know that this value here, this is just a 107 00:05:37,060 --> 00:05:44,550 number, so you can see that by doing type. Execute. Sorry, I didn't print it out. 109 00:05:53,130 --> 00:05:59,530 And so this is a float number, so just a number. The function gets an input and it 111 00:05:59,530 --> 00:06:04,060 generates an output which is defined by the hours variable so whatever is 113 00:06:04,060 --> 00:06:10,170 storing the hours variable, that is the value that the function will output and 115 00:06:10,170 --> 00:06:16,510 yeah, you can do things like you know you can use this output to do other 117 00:06:16,510 --> 00:06:20,860 operations, let's say you want to add ten hours there and you want to print that 119 00:06:20,860 --> 00:06:28,210 output, so expect this to be 11.1666. And so on, and of course 121 00:06:28,210 --> 00:06:34,470 now in your script you can add more functions if you like, you know like that. 123 00:06:34,470 --> 00:06:40,050 Like seconds to hours. You pass seconds there 125 00:06:40,050 --> 00:06:47,310 and here seconds. Return hours and so on and of course this 127 00:06:47,310 --> 00:06:56,639 works separately, so you can say print seconds to hours and past there actually 129 00:06:56,639 --> 00:07:05,449 we have to change this because this would be divided by 3600, and let's say 131 00:07:05,449 --> 00:07:14,400 this number of seconds, execute and you get 2.0 hours and you also get the other 133 00:07:14,400 --> 00:07:21,259 output in here and this one here. Now something important to know is that 135 00:07:21,259 --> 00:07:28,080 these are custom functions and this one here is also function but this is a 137 00:07:28,080 --> 00:07:33,659 built in function, so constant functions are functions created by you and built in 139 00:07:33,659 --> 00:07:39,000 functions are functions that are created by someone else, so in this case print is 141 00:07:39,000 --> 00:07:44,370 created by Python authors and print also has its own code, but it's more a 143 00:07:44,370 --> 00:07:49,680 low-level code and it's actually read-only, so you won't be able to see 145 00:07:49,680 --> 00:07:53,669 the code for print. Yeah, this is an introduction to functions. In the next 147 00:07:53,669 --> 00:07:58,080 lecture I'll show you some more advanced features of functions, so let's see 149 00:07:58,080 --> 00:08:00,529 you there.

1 00:00:00,030 --> 00:00:04,589 Hi and welcome to this new section! In this section you're going to learn about 3 00:00:04,589 --> 00:00:10,250 two very important concepts in programming. These are functions and 5 00:00:10,250 --> 00:00:17,390 conditionals. Functions, functions are used to keep your code more organized so 7 00:00:17,390 --> 00:00:24,029 think of functions as small chunks of code which together build a program that 9 00:00:24,029 --> 00:00:27,240 is what you need to know for now. Functions are useful for other things as 11 00:00:27,240 --> 00:00:31,800 well but you'll understand it as you build the real world programs. In the next 13 00:00:31,800 --> 00:00:36,960 video I'll write a function but that is just a standalone function, so it 15 00:00:36,960 --> 00:00:41,579 doesn't interact with other parts of the code, it's just a function, but when you 17 00:00:41,579 --> 00:00:45,390 see the large applications later on you'll see how the function integrates 19 00:00:45,390 --> 00:00:51,149 with other parts of the code, so that's a good thing of creating reload programs. 21 00:00:51,149 --> 00:00:56,579 That is how you'll learn how to do programming in real life. That's about 23 00:00:56,579 --> 00:01:00,600 functions and then in this section you'll also learn conditionals which basically 25 00:01:00,600 --> 00:01:06,869 are used to have your program make decisions, so if that number is greater 27 00:01:06,869 --> 00:01:12,150 than that do this, if it's not greater than do this other thing, that's 29 00:01:12,150 --> 00:01:17,340 basically the idea, but you'll see it in action, so this is about the introduction 31 00:01:17,340 --> 00:01:21,680 of this section. I'll see you in the other lecture.

1 00:00:01,129 --> 00:00:06,899 Hi again! Let's have one more lecture about errors in Python and this 3 00:00:06,899 --> 00:00:11,429 particular lecture will be about handling errors. Handling errors can be 5 00:00:11,429 --> 00:00:16,590 an advanced concept to digest for now because you're still going through the 7 00:00:16,590 --> 00:00:22,199 basics of Python and you haven't seen any real application yet, but later 9 00:00:22,199 --> 00:00:27,990 will use error handling while we are building real-world applications so 11 00:00:27,990 --> 00:00:32,399 you're going to understand error handling better later on. For now let's 13 00:00:32,399 --> 00:00:35,670 just focus on the syntax and try to understand as much as you can 15 00:00:35,670 --> 00:00:42,899 I'll go and do an example here which I mentioned earlier. Let's say we have a 17 00:00:42,899 --> 00:00:54,090 function that does division between two given numbers like that. Return a divided 19 00:00:54,090 --> 00:00:59,719 by b and then you call the function here. Divide 1, 2. In this case the 21 00:01:05,640 --> 00:01:10,619 function will try to divide 1 by 2. And let me print out the output so that 23 00:01:10,619 --> 00:01:20,159 we can see it on the terminal. Go to the terminal and execute the script. So you 25 00:01:20,159 --> 00:01:28,460 get you get 0.5. Now that's good. However if the user enters let's say 27 00:01:28,460 --> 00:01:35,790 zero there like that, execute and your program will crash so it will show an 29 00:01:35,790 --> 00:01:41,939 error. Now this one here is an example of a longer error message that I mentioned 31 00:01:41,939 --> 00:01:45,750 previously in the previous videos that you might have more than one, more 33 00:01:45,750 --> 00:01:54,869 than one error in your traceback, so for instance this says line 4 at this line 35 00:01:54,869 --> 00:02:01,259 here. So that line is where Python captured the error at first 37 00:02:01,259 --> 00:02:06,360 so basically Python was trying to execute this line but it couldn't do it, 39 00:02:06,360 --> 00:02:10,709 it didn't manage to do it because this line was trying to get the information 41 00:02:10,709 --> 00:02:15,460 from this function and this function was trying to do this 43 00:02:15,460 --> 00:02:22,280 mathematical operation using zero after the division so that is not possible and 45 00:02:22,280 --> 00:02:27,950 Python is pointing that out here. So that's the main error in line two 47 00:02:27,950 --> 00:02:32,510 in this expression so that's where you should focus, however when you ask 49 00:02:32,510 --> 00:02:36,590 questions you should include the entire error message in your question 51 00:02:36,590 --> 00:02:43,550 as I mentioned previously. So back to handling errors now. What I'm 53 00:02:43,550 --> 00:02:49,850 trying to say here is that you know you have other functions here and other 55 00:02:49,850 --> 00:02:57,320 lines of code that you want to execute, that you want Python to execute, but if 57 00:02:57,320 --> 00:03:04,720 the user passed this zero number here the other lines would not be executed 59 00:03:04,720 --> 00:03:09,680 so your program would crash and you don't want that and the way to avoid 61 00:03:09,680 --> 00:03:17,720 that is by using try and accept so basically you try to capture the 63 00:03:17,720 --> 00:03:24,170 exception, to handle the exception. The way to do that is quite easy. 65 00:03:24,170 --> 00:03:33,860 You say try and return a/b, so this has to be indented like that so try is indented 67 00:03:33,860 --> 00:03:40,160 because it's under the function definition. And then return is indented 69 00:03:40,160 --> 00:03:49,190 because it's under the try expression. Then you have except, execute so this 71 00:03:49,190 --> 00:03:54,470 has to be on the same indentation level with try, they are the same block, so 73 00:03:54,470 --> 00:04:02,090 except if there is an exception. What you want to do is print out: "You are 75 00:04:02,090 --> 00:04:07,540 dividing by zero", or "is this meaningless". So let me try 77 00:04:16,299 --> 00:04:26,380 this now and you get: "Zero division is meaningless" and none, oh sorry I meant 79 00:04:26,380 --> 00:04:34,420 to do here return, not print. I explained you why you get none there so you 81 00:04:34,420 --> 00:04:42,940 got none as an output because what the function did was its tried to do 83 00:04:42,940 --> 00:04:48,160 this expression but it got an error so it ignores this line, it doesn't 85 00:04:48,160 --> 00:04:54,880 execute it and then it goes to the next line. So this line is executed when 87 00:04:54,880 --> 00:05:01,540 this is not executed and so it printed out: "Zero division is meaningless", but it 89 00:05:01,540 --> 00:05:06,010 also printed out none because when you execute a function that doesn't have a 91 00:05:06,010 --> 00:05:10,450 return statement such as in this case we had the print statement here, the print 93 00:05:10,450 --> 00:05:15,820 function not the return statement, in that case if the function is not returning 95 00:05:15,820 --> 00:05:23,440 anything it can have a print function or other function as well, but if it 97 00:05:23,440 --> 00:05:29,229 doesn't have a return statement then it will print out none, so basically 99 00:05:29,229 --> 00:05:33,520 it executes the other procedures such as the print statement, it prints out the 101 00:05:33,520 --> 00:05:37,690 statement but if it doesn't have a return statement it doesn't, it prints 103 00:05:37,690 --> 00:05:43,030 out none. Anyway save this now, execute again and in this case you get only this 105 00:05:43,030 --> 00:05:48,729 zero division is meaningless printed out there. So basically if you had other 107 00:05:48,729 --> 00:05:57,280 lines of code here like that, those would be executed as well and that happens by 109 00:05:57,280 --> 00:06:03,160 using the try and except block who which make sure that the code flow continues. 111 00:06:03,160 --> 00:06:11,050 So while the important thing to note is that it is advisable to actually here use 113 00:06:11,050 --> 00:06:18,120 the exact name of the error that you want to accept, so 115 00:06:19,350 --> 00:06:27,340 Zero Division Error and as you see these got turned into blue which means that 117 00:06:27,340 --> 00:06:33,370 this is actually a Python keyword, is recognized by Python and in that case if 119 00:06:33,370 --> 00:06:41,560 you exact you this you get the same output actually like that or if you pass 121 00:06:41,560 --> 00:06:46,650 a number there that it is possible to get a division from, you'll get that. 123 00:06:46,650 --> 00:06:53,020 Sorry about the backslash. I typed that by mistake on my terminal. Execute 125 00:06:53,020 --> 00:06:56,650 again so you get this. And so what I'm trying to say about the zero division 127 00:06:56,650 --> 00:07:01,090 error is that you know sometimes you might get other types of errors in your 129 00:07:01,090 --> 00:07:07,930 code, other types of exceptions. Let's say you have a name error there 131 00:07:07,930 --> 00:07:12,370 and you are saying that except all errors when you don't pass this you 133 00:07:12,370 --> 00:07:17,919 you're basically including all types of errors there and that is a bit dangerous for your 135 00:07:17,919 --> 00:07:22,960 code because you know you might have problems that you don't notice and 137 00:07:22,960 --> 00:07:27,789 basically you are ignoring that, but you shouldn't. So you should be specific 139 00:07:27,789 --> 00:07:32,830 there, explicit like that. If there are other types of errors such as a name error, 141 00:07:32,830 --> 00:07:38,349 that name error will crash your program, so you know what's going on. 143 00:07:38,349 --> 00:07:42,760 You need to be specific. If you want to handle that error too, then 145 00:07:42,760 --> 00:07:47,380 you can add another exception here. Except name error for instance. Yeah, 147 00:07:47,380 --> 00:07:52,389 that's about handling errors in Python. I hope this makes sense! I hope I explained 149 00:07:52,389 --> 00:07:58,330 this well! And yeah, this is about errors. I'll talk to you in the next lectures. 151 00:07:58,330 --> 00:08:00,000 See you!

1 00:00:00,260 --> 00:00:06,089 Great, welcome again to this new video. This is the third video about errors. We 3 00:00:06,089 --> 00:00:10,500 talked about syntax errors, we talked about exceptions, and now we're going to 5 00:00:10,500 --> 00:00:15,179 talk about how to fix an error when you don't understand the message, so let's 7 00:00:15,179 --> 00:00:23,189 focus on this error, a zero division error. In case you were good in mathematics you 9 00:00:23,189 --> 00:00:26,789 could easily fix this error so you you'll be able to understand that you 11 00:00:26,789 --> 00:00:32,820 cannot divide c by, you cannot divide a number by 0 so you'd fix this by 13 00:00:32,820 --> 00:00:39,090 removing this expression here. However if you were not that good in mathematics you 15 00:00:39,090 --> 00:00:43,590 may find this difficult to understand. In that case the fastest way to fix this 17 00:00:43,590 --> 00:00:51,360 error is by copying this line here. Control C, so select it copy it with ctrl 19 00:00:51,360 --> 00:01:02,510 C or right click and copy there and then go to Google. Just paste it. Now on Google 21 00:01:02,510 --> 00:01:08,909 this got around a hundred thousand results so Python is very popular and 23 00:01:08,909 --> 00:01:16,040 you'll get a solution for almost every problem that you'll get with Python 25 00:01:16,040 --> 00:01:21,810 so before looking at documentation or asking a question somewhere it's very 27 00:01:21,810 --> 00:01:26,070 likely that someone else has had your issue before and i have asked a question 29 00:01:26,070 --> 00:01:29,640 about that and there is a solution about that as well. 31 00:01:29,640 --> 00:01:37,280 And a very good question and answer website is stackoverflow.com and 33 00:01:37,280 --> 00:01:41,640 almost always when you search for an error on Google the first results will 35 00:01:41,640 --> 00:01:51,299 be from stackoverflow and so someone has asked a question with this title. It says 37 00:01:51,299 --> 00:01:55,680 I faced an error when I run the program using Python. So it's the same things as 39 00:01:55,680 --> 00:02:02,820 error as you like that. How to avoid that error? And if it also talks about the 41 00:02:02,820 --> 00:02:06,110 desired output. And there are two answers for this 43 00:02:09,899 --> 00:02:16,170 question. tThe answer with this green mark here is the accepted answering and it 45 00:02:16,170 --> 00:02:22,800 has and it has the most up votes so 11 and this has 2 down votes some minus 2. 47 00:02:22,800 --> 00:02:27,209 Actually the difference between up votes and down votes is in the favor of 49 00:02:27,209 --> 00:02:33,420 down votes and so these are two different answers that you can look at. Usually you 51 00:02:33,420 --> 00:02:38,519 want to look at the accepted answer that has the solution, however in this case 53 00:02:38,519 --> 00:02:45,209 this also has the explanation it says you cannot divide by 0. This causes 55 00:02:45,209 --> 00:02:50,549 Python to raise an error. That's single good answer and I think it didn't 57 00:02:50,549 --> 00:02:57,209 deserve to get to have this balance of votes, but this one gives a 59 00:02:57,209 --> 00:03:02,910 solution on how to handle an error and that takes us to another concept which 61 00:03:02,910 --> 00:03:08,489 is handling errors in Python. So let's say you have a program you have a 63 00:03:08,489 --> 00:03:15,000 function that gets two input values and then it divides those two input values. 65 00:03:15,000 --> 00:03:21,959 However sometimes the user may pass zero as as a second input and in that 67 00:03:21,959 --> 00:03:25,170 case if you divide, let's say the first value would be 2 and the second value 69 00:03:25,170 --> 00:03:34,019 would be 0, your program would crash and if you want you can use exception 71 00:03:34,019 --> 00:03:38,639 handling to actually avoid that program from crashing. And you can do that with a 73 00:03:38,639 --> 00:03:44,099 try and accept statements. Anyway we'll cover that in the next lectures in this 75 00:03:44,099 --> 00:03:51,450 section. So this was about searching for an error on Google and you can 77 00:03:51,450 --> 00:03:56,069 easily find the solution to that as you see. These are very clear questions. It's 79 00:03:56,069 --> 00:04:01,319 a big community and everyone can vote up and down and can comment and so 81 00:04:01,319 --> 00:04:07,380 basically the answers are very accurate. However you'll not always find an answer on 83 00:04:07,380 --> 00:04:11,060 Google. In that case it's time to ask your own 85 00:04:11,060 --> 00:04:17,389 question, so the first thing is again you check if you understand the error and 87 00:04:17,389 --> 00:04:22,220 fix it if you understand it. The second thing is you do a search on Google and 89 00:04:22,220 --> 00:04:27,229 if the first to fail to solve your problem, then it's time to ask a question. 91 00:04:27,229 --> 00:04:34,820 And you can ask a question either inside the course, so you can, while watching a 93 00:04:34,820 --> 00:04:40,669 video you can browse Q&A which stands for question and answer and you can do a 95 00:04:40,669 --> 00:04:44,840 quick search if you find an existing answer to your question here and if you 97 00:04:44,840 --> 00:04:48,349 cannot find it then you can ask a question, or you can ask a question on 99 00:04:48,349 --> 00:04:55,669 stackoverflow. You can use this button here, ask a question and I'll be happy to 101 00:04:55,669 --> 00:05:00,620 help you here on the course interface Q&A section. 103 00:05:00,620 --> 00:05:06,020 Or other people can also help you own stackoverflow, however something is very 105 00:05:06,020 --> 00:05:12,289 important to know. The structure of your question is very important on getting a 107 00:05:12,289 --> 00:05:18,169 good answer. You know sometimes there are very bad questions like let's 109 00:05:18,169 --> 00:05:23,750 say my code is not working how do I fix this and that's all. With that very 111 00:05:23,750 --> 00:05:28,759 little information is very hard to get a good answer so it's very important to 113 00:05:28,759 --> 00:05:33,919 ask a good question and I'll show you how to ask a good programming question 115 00:05:33,919 --> 00:05:38,000 in the next lecture. So that's a very important lecture as well. See you there!

1 00:00:00,030 --> 00:00:04,020 Hey, hi again and welcome to yet another lecture. In this lecture I'll show you 3 00:00:04,020 --> 00:00:09,090 how to ask a good programming question. So I mentioned in the previous lecture 5 00:00:09,090 --> 00:00:14,089 asking a good programming question is very important to get a good answer and 7 00:00:14,089 --> 00:00:21,109 let me first show you what a bad programming question. For instance 9 00:00:21,109 --> 00:00:28,410 I'm going to click on ask question and here is the title of a question. A bad 11 00:00:28,410 --> 00:00:33,420 programming question would have a very generic title like that. Here is the body 13 00:00:33,420 --> 00:00:36,960 of the question where you have to describe your question in detail. 15 00:00:36,960 --> 00:00:48,239 Some people do they just say: I got an error when trying to two numbers and they 17 00:00:48,239 --> 00:00:55,350 just post the question. A better question would be to include the error, the code 19 00:00:55,350 --> 00:01:00,050 there that you executed like that. However that is also not enough because 21 00:01:04,140 --> 00:01:09,810 you also need to show the error message. So let me delete this, and a good program 23 00:01:09,810 --> 00:01:14,509 in question would be We're talking about questions that have an error, 25 00:01:14,509 --> 00:01:20,820 questions that talk about an error that you got in your code. So this is your 27 00:01:20,820 --> 00:01:27,780 code. A good title would be to include the error message, so that one would be a 29 00:01:27,780 --> 00:01:32,070 good fit. If it's a very long message then you can also you can choose to 31 00:01:32,070 --> 00:01:37,829 include only the name of the error without that and then a good question woulb 33 00:01:37,829 --> 00:01:50,460 be: Hi, I run the following code and expected to get division in the last print 35 00:01:50,460 --> 00:01:55,520 statement, but I got an error. Here is my code, so you put the code 37 00:02:01,030 --> 00:02:08,590 there, your entire script. Don't worry if your question is long. It's better to 39 00:02:08,590 --> 00:02:19,950 be long than to be incomplete and here is the error. Here make sure to include 41 00:02:19,950 --> 00:02:28,510 your entire errors trace back including the output as well. So from this 43 00:02:28,510 --> 00:02:34,209 line of the command line up to the next line so this entire thing goes to your 45 00:02:34,209 --> 00:02:43,750 question. Just copy it. Don't worry if it's long. Can you help? So that'd be a good 47 00:02:43,750 --> 00:02:48,099 programming question. Now this is still missing something very important and 49 00:02:48,099 --> 00:02:52,989 that is the highlighting of the code. You need to select the code and click on 51 00:02:52,989 --> 00:03:07,870 this icon here. The error as well. And let me pose the question. External links must 53 00:03:07,870 --> 00:03:14,560 provide free educational content, just click on proceed and here is the question. 55 00:03:14,560 --> 00:03:18,430 Here is how it looks like on the other end. So this question has 57 00:03:18,430 --> 00:03:21,940 four good elements that make it a good question. 59 00:03:21,940 --> 00:03:29,590 The first element is that the poster is mentioning what he or she expected to 61 00:03:29,590 --> 00:03:36,250 get as output from the script that here they were running so it says I was 63 00:03:36,250 --> 00:03:39,760 expecting to get the division in the last print statement which is this one 65 00:03:39,760 --> 00:03:44,620 here, but I got an error so the first thing is you need to include the 67 00:03:44,620 --> 00:03:48,250 expected output, you need to explain what you were expecting because 69 00:03:48,250 --> 00:03:53,440 otherwise if you don't explain what you were expecting the other person who 71 00:03:53,440 --> 00:04:01,780 wants to help you doesn't know the goal of your code or of your questions so it 73 00:04:01,780 --> 00:04:05,890 doesn't know how to help you to reach to that goal. So expected output is the first 75 00:04:05,890 --> 00:04:08,830 thing. The second thing is you need to include your entire code 77 00:04:08,830 --> 00:04:15,970 and make sure that you include your code as text. It's best to use text, 79 00:04:15,970 --> 00:04:22,360 rather than screenshots because text, the person who wants to help you can copy 81 00:04:22,360 --> 00:04:29,500 your code and run it all their Python interpreter, but if you includes 83 00:04:29,500 --> 00:04:35,940 screenshots they are images and it's hard for other people to try out your code 85 00:04:35,940 --> 00:04:40,060 If you ask this on stackoverflow your 87 00:04:40,060 --> 00:04:44,530 question would get closed because if you ask it or we're using a screenshot 89 00:04:44,530 --> 00:04:49,660 rather than the text version of your code, the question will get closed 91 00:04:49,660 --> 00:04:55,620 because there are very strong rules in stackoverflow to have a high-quality 93 00:04:55,620 --> 00:05:01,690 question and answer site. So that's that second element. The third element is you 95 00:05:01,690 --> 00:05:09,730 need to include your entire screenshot, entire error traceback, sorry, so from the 97 00:05:09,730 --> 00:05:14,770 beginning up to the end. So that was the third element, and the last element, the 99 00:05:14,770 --> 00:05:19,870 fourth element is you need to highlight your code just like that. You see this is 101 00:05:19,870 --> 00:05:27,400 much more visible and easier for others to troubleshoot. So the course interface 103 00:05:27,400 --> 00:05:32,440 has that function there that you can highlight your code. On stackoverflow 105 00:05:32,440 --> 00:05:37,169 you also have that capability so just go to ask question, you write your code here, 107 00:05:37,169 --> 00:05:46,780 highlight it and then use these curly brackets. Yeah, that's it. If you ask a 109 00:05:46,780 --> 00:05:51,190 good questions the odds are that you're going to get a good answer as well. So I 111 00:05:51,190 --> 00:05:55,810 hope this makes sense and I hope I showed you something that you didn't know and 113 00:05:55,810 --> 00:06:00,000 I'll talk to you later. See you!

1 00:00:01,429 --> 00:00:06,240 Hi again and welcome to this new lecture! In the previous lecture we talked about 3 00:00:06,240 --> 00:00:13,320 errors in general and I focused on syntax errors which is one of the two 5 00:00:13,320 --> 00:00:17,250 types of errors that you have in Python. So you have syntax errors and you have 7 00:00:17,250 --> 00:00:23,640 exceptions. Now we're going to talk about exceptions in Python, so every other type 9 00:00:23,640 --> 00:00:29,699 of error that is not a syntax error is an exception. And often all errors, 11 00:00:29,699 --> 00:00:35,160 syntax errors and exceptions they are referred to as errors so you're going to 13 00:00:35,160 --> 00:00:41,219 hear this all over the place. Now I have a new script here that I created for 15 00:00:41,219 --> 00:00:46,050 this lecture. Try to guess what I'm going to get as 17 00:00:46,050 --> 00:00:53,340 output when I execute this script, so I have a equal to 1, n equals to characters 2. 19 00:00:53,340 --> 00:01:04,430 Print int 2.5 and print a plus b. So guess what I'm going to get for a moment. 21 00:01:04,430 --> 00:01:17,369 Okay, now let me run the script Python 3. Errors.py. File errors.py line 4 23 00:01:17,369 --> 00:01:28,020 which is the last line, this one. We get a syntax error, invalid syntax. Now this 25 00:01:28,020 --> 00:01:31,979 can be very confusing for you now because you know you're looking at the 27 00:01:31,979 --> 00:01:40,680 print a plus b expression, but you don't see any error there. So for a beginner of 29 00:01:40,680 --> 00:01:49,020 this can be quite frustrating but try to look back on the left of arrow here, so 31 00:01:49,020 --> 00:01:54,509 think of the arrow that the arrow is pointing at the token and token has not 33 00:01:54,509 --> 00:01:59,670 been written correctly in the script, so in this case you know the problem 35 00:01:59,670 --> 00:02:07,600 here is that this line here it has an open bracket, round bracket 37 00:02:07,600 --> 00:02:13,920 and than it has an int function, and then the int function has its own brackets that is 39 00:02:13,920 --> 00:02:19,360 wrapping inside its input, so these are the brackets of the int function, but the 41 00:02:19,360 --> 00:02:24,640 print function doesn't have a closing bracket. What you did instead, what I did 43 00:02:24,640 --> 00:02:30,760 actually, what I did is that instead of putting a bracket there I actually wrote 45 00:02:30,760 --> 00:02:38,050 another print function so Python was expecting a closing round 47 00:02:38,050 --> 00:02:43,450 bracket, but I wrote I typed in a print function. That's why this is saying that 49 00:02:43,450 --> 00:02:49,420 this print function is not in the correct position. That's the idea. 51 00:02:49,420 --> 00:02:55,030 So always when you see this arrow first look at this line event look before that 53 00:02:55,030 --> 00:03:03,940 also. Sorry about this! So always when you see this arrow here, first look at this 55 00:03:03,940 --> 00:03:09,610 line here but also don't forget that the problem might also be before this 57 00:03:09,610 --> 00:03:14,340 line. Okay, so that was about the syntax error. 59 00:03:14,340 --> 00:03:19,299 I'll explain why I talked about this syntax error here let me execute this 61 00:03:19,299 --> 00:03:24,850 again. So the syntax error was fixed now, but we still have another error. So the 63 00:03:24,850 --> 00:03:29,650 reason I included a syntax error in my code was to show you that Python 65 00:03:29,650 --> 00:03:36,190 actually first checks for syntax errors so basically it parses the code, it looks 67 00:03:36,190 --> 00:03:43,060 for syntax errors, it doesn't execute the code yet. So when I executed Python 3 69 00:03:43,060 --> 00:03:47,170 errors that's why i in here the code was not executed but the interpreter just 71 00:03:47,170 --> 00:03:53,950 checks for syntax errors, it doesn't check for exceptions just yet. So first 73 00:03:53,950 --> 00:03:56,890 you need to fix the syntax errors and that's what we did here. We added 75 00:03:56,890 --> 00:04:02,610 these brackets and we fixed the syntax errors. Now Python is throwing out an exception and 77 00:04:02,610 --> 00:04:08,620 let's, here is where I executed the code and see the next line we have number two 79 00:04:08,620 --> 00:04:14,380 there which is coming from the output of this line here, so from line three we 81 00:04:14,380 --> 00:04:19,239 got the output correctly. So basically again Python executes the script from top 83 00:04:19,239 --> 00:04:22,810 to bottom if it doesn't find 85 00:04:22,810 --> 00:04:28,930 syntax errors. If it finds syntax errors it doesn't execute anything. So 2 is 87 00:04:28,930 --> 00:04:36,360 printed out and then you get this trace back of the error which starts there and 89 00:04:36,360 --> 00:04:44,680 ends in here that's a block of the error. Sometimes the errors may have more than 91 00:04:44,680 --> 00:04:50,950 one type of error. So in this case we have only one type of error which is 93 00:04:50,950 --> 00:04:56,830 a type error, but you may have multiple blocks here. However the most important 95 00:04:56,830 --> 00:05:02,710 error that you must focus on is the lost line of the error, so the last block of 97 00:05:02,710 --> 00:05:08,520 of the error. In this case we have only one block so we're focused on that. 99 00:05:08,520 --> 00:05:16,570 And line 4 which is this one in here. This is the line. Again the line is printing out 101 00:05:16,570 --> 00:05:21,520 just like in the case of syntax error. And you have a type of the error here 103 00:05:21,520 --> 00:05:26,920 which is a type error. So what's a type error? A type error means that there is 105 00:05:26,920 --> 00:05:35,530 something wrong with one of your object types in your script, and you have the 107 00:05:35,530 --> 00:05:42,220 description here. Unsupported operand type for plus so this is trying to say 109 00:05:42,220 --> 00:05:48,130 that the plus operator has an unsupported type so the plus operator in 111 00:05:48,130 --> 00:05:52,690 other words doesn't support one of the types that you have given to it, so it's 113 00:05:52,690 --> 00:05:59,730 either the type of variable a or the type of variable b. So it says int and 115 00:05:59,730 --> 00:06:06,730 string, so it doesn't specifically say whether int or string is an object but 117 00:06:06,730 --> 00:06:12,250 it says that you cannot use a plus operator with an integer and a string. 119 00:06:12,250 --> 00:06:18,670 And that's logically wrong because you cannot add a number to some 121 00:06:18,670 --> 00:06:24,150 text. That's what Python does not understand so it throws a type error. 123 00:06:24,150 --> 00:06:30,500 So exceptions are like logical errors and you need to use your logic now to 125 00:06:30,500 --> 00:06:35,720 fix the error. And you use your logic by carefully inspecting the error and 127 00:06:35,720 --> 00:06:40,790 that's what we did. So what we want to do, we want to fix 129 00:06:40,790 --> 00:06:47,390 this. Now it's up to me whether I meant to concatenate these two objects 131 00:06:47,390 --> 00:06:54,800 or do a mathematical addition operation. So let's say if I was intending to 133 00:06:54,800 --> 00:07:01,190 do an addition between these two numbers then I would have to convert b to a float 135 00:07:01,190 --> 00:07:09,710 or an integer. Save that, execute, and yeah in this case you 137 00:07:09,710 --> 00:07:14,840 don't get any error. You get 2 printed out from the second, from the third line 139 00:07:14,840 --> 00:07:22,310 and 3.0 from the last line that we have just fixed. However if my intention was 141 00:07:22,310 --> 00:07:29,690 to actually print out the concatenation between these two strings, instead of 143 00:07:29,690 --> 00:07:36,310 converting b to a float, I would have to convert a to a string. 145 00:07:36,310 --> 00:07:42,980 In this case I would get the text 12. 12, so that would be 147 00:07:42,980 --> 00:07:50,060 a string object, not a number. Even though here it shows as a number it's just how 149 00:07:50,060 --> 00:07:57,169 the terminal prints it out. So again these are errors that occur in runtime, so when 151 00:07:57,169 --> 00:08:03,110 the script executes. Syntax errors are parsing errors so the interpreter tries 153 00:08:03,110 --> 00:08:07,640 to understand whether the script is syntactically correct, whether 155 00:08:07,640 --> 00:08:13,910 you have followed the Python syntax rules. So you need a bracket, 157 00:08:13,910 --> 00:08:18,560 a closing bracket for an opening bracket. You need a closing quote after the opening 159 00:08:18,560 --> 00:08:26,570 quote and so on. Now there are also other types of exceptions, not only type 161 00:08:26,570 --> 00:08:34,030 error. You know you may have a name error. Let's say here instead of printing out 163 00:08:34,030 --> 00:08:43,330 that, we print out c. Save, execute and here is the trace back. 165 00:08:43,330 --> 00:08:50,970 Again 2 was printed out from the third line and the trace back says line 4 at 167 00:08:50,970 --> 00:09:00,730 print c, name error name c is not defined. So again this is not a syntax 169 00:09:00,730 --> 00:09:04,750 error because you haven't made any mistakes with the syntax. You know you have 171 00:09:04,750 --> 00:09:10,120 this variable name which is correct, you have brackets opening, round brackets 173 00:09:10,120 --> 00:09:14,890 and closing round bracket, so everything is syntactically correct both this c 175 00:09:14,890 --> 00:09:20,170 object Python doesn't know this. You haven't defined this c variable so 177 00:09:20,170 --> 00:09:23,920 Python doesn't know what to print out. You know python is able to print out a 179 00:09:23,920 --> 00:09:30,940 because it knows that a refers to the 1 to integer 1 and so it prints out 181 00:09:30,940 --> 00:09:36,790 integer 1, but c doesn't have anything so you get this name error and whenever 183 00:09:36,790 --> 00:09:42,520 you get a name error you know that this name here has not been defined by you so 185 00:09:42,520 --> 00:09:48,490 to fix this you may want to define c like that and execute and you don't get 187 00:09:48,490 --> 00:09:54,160 any error. You may also have other types of errors such as c divided by 0. 189 00:09:54,160 --> 00:10:02,080 See what you get. Zero division error division by 0. That's the 191 00:10:02,080 --> 00:10:07,300 description of this error so division by 0 is not mathematically possible or 193 00:10:07,300 --> 00:10:13,330 meaningful and since python is based on mathematics it throws an error in 195 00:10:13,330 --> 00:10:17,200 and you need to fix that. You need to remove that expression that divides by 0. 197 00:10:17,200 --> 00:10:25,720 Yeah, that's about errors in Python. I hope you understood a great deal of this 199 00:10:25,720 --> 00:10:30,820 lecture and the previous lecture as well. So it's relatively easy to fix errors, 201 00:10:30,820 --> 00:10:35,800 however sometimes there are errors that you might have 203 00:10:35,800 --> 00:10:41,620 difficulties understanding and fixing them so later for example we're going to 205 00:10:41,620 --> 00:10:45,220 work on libraries and sometimes libraries they have different kinds of 207 00:10:45,220 --> 00:10:49,900 errors, however nothing to worry about because there are other things that you 209 00:10:49,900 --> 00:10:53,050 can do for an arrow that you don't understand. 211 00:10:53,050 --> 00:10:58,000 And I'll talk about that in the next lecture, so I'll see you there!

1 00:00:00,319 --> 00:00:06,270 Hey welcome to this new lecture! This is the most important lecture you have had 3 00:00:06,270 --> 00:00:12,240 so far in this course, so please try to make the most of it and this is actually 5 00:00:12,240 --> 00:00:15,780 a new video that I am adding to the course. I didn't have this lecture a few 7 00:00:15,780 --> 00:00:22,320 times ago so I had this quite a while after I published the course and until 9 00:00:22,320 --> 00:00:26,550 now I had explained this concept, so the errors little by little in other 11 00:00:26,550 --> 00:00:32,610 lectures but I felt that was not enough and I was seeing that students were 13 00:00:32,610 --> 00:00:37,140 still having difficulties in understanding and dealing with errors in 15 00:00:37,140 --> 00:00:44,070 Python so I decided to make a dedicated lecture for errors in Python. So here we 17 00:00:44,070 --> 00:00:48,629 are and I said this is the most important lecture because you know we 19 00:00:48,629 --> 00:00:54,510 we learnt about functions and strings and numbers until now in the previous 21 00:00:54,510 --> 00:01:00,480 videos and these are individual concepts that you know you'll learn, now or later you'll 23 00:01:00,480 --> 00:01:05,760 learn functions and strings and etc, but if you don't know how to read an error 25 00:01:05,760 --> 00:01:11,220 how to to understand an error and deal with it if you don't know that you will 27 00:01:11,220 --> 00:01:15,930 have trouble dealing with everything every other object like functions and 29 00:01:15,930 --> 00:01:22,560 streams and numbers etc. So understanding and error and knowing how to deal with 31 00:01:22,560 --> 00:01:28,350 it, how to fix it is very important and even the most experienced programmers 33 00:01:28,350 --> 00:01:34,140 they make errors in their programs. The difference is that they know how to read 35 00:01:34,140 --> 00:01:39,420 these errors. How to understand and fix them, but everyone makes errors. So if 37 00:01:39,420 --> 00:01:44,460 an error shows in your program don't panic just for all the instructions that 39 00:01:44,460 --> 00:01:48,840 I'll give you in this video on how to fix the error so that's what this 41 00:01:48,840 --> 00:01:54,930 lecture is about. So what is an error anyway? An error in a program is a bug 43 00:01:54,930 --> 00:02:00,509 that causes the program to function incorrectly. Now in Python we have 45 00:02:00,509 --> 00:02:06,229 basically two types of errors. We have syntax errors and we have exceptions. 47 00:02:06,229 --> 00:02:10,950 Let's first focus on syntax errors and let's forget about exceptions. We'll go 49 00:02:10,950 --> 00:02:16,840 to exceptions after we explain syntax errors. I have this code here and 51 00:02:16,840 --> 00:02:23,019 actually this is a Python file. This is the icon showing on a Mac so currently 53 00:02:23,019 --> 00:02:27,909 I am on a Mac computer but that doesn't make the slightest difference. No matter 55 00:02:27,909 --> 00:02:33,280 where you are on Linux Windows or Mac everything is the same. So I have the 57 00:02:33,280 --> 00:02:37,750 terminal here and let me go ahead and execute this program. This has a few 59 00:02:37,750 --> 00:02:44,890 errors so let me show them. On Mac you can call Python 3 with the python3 61 00:02:44,890 --> 00:02:49,870 command, on Windows you can just call python or whatever command you are 63 00:02:49,870 --> 00:02:56,049 using. You can also use any editor that you like and so errors.py is the 65 00:02:56,049 --> 00:03:07,290 name I gave to the script, execute. So this is now an example of a syntax error 67 00:03:07,290 --> 00:03:14,230 and this is the entire body of the error message and this is very important, so 69 00:03:14,230 --> 00:03:19,450 whenever you get an error the first advice I give you is don't panic just 71 00:03:19,450 --> 00:03:23,730 focus on the error. Read it line by line just like you're reading a poem or 73 00:03:23,730 --> 00:03:32,739 whatever so the first line of the error points you to the name of the file that 75 00:03:32,739 --> 00:03:37,840 has the error. In this case is errors.py. Then you have a comma and after 77 00:03:37,840 --> 00:03:40,620 the comma you have the line where the error occurred. 79 00:03:40,620 --> 00:03:47,169 So it's line 3 and you can see that line 3 is this one here but you also have for 81 00:03:47,169 --> 00:03:53,379 your convenience Python prints out the line in the terminal so int 9. Here is 83 00:03:53,379 --> 00:03:59,199 where the error is and just after that you have the type of the error so it's a 85 00:03:59,199 --> 00:04:03,849 syntax error, you also have other types of errors such as name error, type error, 87 00:04:03,849 --> 00:04:07,780 but those are exceptions and I'll explain later why we call them 89 00:04:07,780 --> 00:04:12,519 exceptions, so this is one type of error a syntax error and the others are 91 00:04:12,519 --> 00:04:18,900 exceptions. So this is the type and then you have the description after the colon. 93 00:04:18,900 --> 00:04:24,990 Sometimes the description is more specific more detailed. This time is just 95 00:04:24,990 --> 00:04:29,870 invalid syntax. So you have to figure out where 97 00:04:29,870 --> 00:04:36,259 you did some error where you missed some syntax of your program. 99 00:04:36,259 --> 00:04:45,080 And you also have this arrow here pointing upwards and the arrow points you even at the 101 00:04:45,080 --> 00:04:51,770 token that the error is occurring or at the end of the token, so a token is you 103 00:04:51,770 --> 00:04:58,190 know, this is the token in this case 9. So it can be a number, it can be string, 105 00:04:58,190 --> 00:05:04,400 anything, so at this point this is pointing at this, at the token but 107 00:05:04,400 --> 00:05:11,780 it could also be like that. 999 save the script, execute. In this 109 00:05:11,780 --> 00:05:16,220 case you see that it's pointing you at the end of the token. So here's, around 111 00:05:16,220 --> 00:05:21,729 here you have an error now and I know that int is actually a function and 113 00:05:21,729 --> 00:05:29,780 functions important they need to have brackets so you need to pass 999 inside 115 00:05:29,780 --> 00:05:42,650 brackets like that and you leave that. Save and execute again. All right, you've 117 00:05:42,650 --> 00:05:49,729 got another error but don't panic again. This is my advice always, instead 119 00:05:49,729 --> 00:05:54,979 read the error it says file errors.py the file line 5, oh line 5 this time. 121 00:05:54,979 --> 00:06:02,210 So it's not line 3 anymore which means that line 3 was fixed so what Python is 123 00:06:02,210 --> 00:06:06,949 doing is it's going through all the lines one by one from top to bottom, it 125 00:06:06,949 --> 00:06:11,330 checks the first line it says: "Oh it's fine, no error there". Goes to the next 127 00:06:11,330 --> 00:06:16,130 line no error, goes through the third line, no error this time, fourth line is 129 00:06:16,130 --> 00:06:21,860 also fine, and fifth line has an error so again it's a syntax error and this one 131 00:06:21,860 --> 00:06:28,630 is more specifically described so missing parentheses in call to print. 133 00:06:28,630 --> 00:06:33,560 Note that you get this error only if you are on Python 3. If you are on Python 2 135 00:06:33,560 --> 00:06:40,810 this won't be an error because in Python 2 print was a statement and was not 137 00:06:40,810 --> 00:06:46,210 function so with statements like return or print in Python - you didn't 139 00:06:46,210 --> 00:06:49,150 have to pass brackets. This syntax would be correct. 141 00:06:49,150 --> 00:06:56,190 So again this arrow here is pointing you and the token so we just add 143 00:06:56,190 --> 00:07:04,810 brackets there, ctrl s to save the script and execute again. This time we don't get 145 00:07:04,810 --> 00:07:09,280 any error so the script executed fine and print it out the output here. 147 00:07:09,280 --> 00:07:15,400 1 2 3 so we had 3 print functions printing out output. This doesn't return 149 00:07:15,400 --> 00:07:21,340 any output because we're not printing anything so this just gets the function 151 00:07:21,340 --> 00:07:26,410 input and produces some output but doesn't print anything. If you want to 153 00:07:26,410 --> 00:07:30,550 print it, you want to pass the print statement function there. There could 155 00:07:30,550 --> 00:07:36,940 also be other types of syntax errors and you know such as you want to define a 157 00:07:36,940 --> 00:07:44,800 least 1, 2, 3, but instead of closing it with a square brackets, you use 159 00:07:44,800 --> 00:07:50,260 a round bracket instead like that. Save the script and execute and you see that 161 00:07:50,260 --> 00:07:58,030 you got a syntax error, invalid syntax at line 5 which is this one in here. Again 163 00:07:58,030 --> 00:08:04,780 the arrow points you at the token so you need to figure out how to fix this round 165 00:08:04,780 --> 00:08:11,020 bracket here and you know that. You need to close it with a square bracket so 167 00:08:11,020 --> 00:08:15,760 that should fix the issue. So these are Ao that's about syntax errors. They are 169 00:08:15,760 --> 00:08:22,000 very easy to fix. In the next lecture I will explain exceptions so see you there!

1 00:00:00,709 --> 00:00:08,580 Hey, hello! Let's look at dictionaries in this lecture. This far we've looked at strings 3 00:00:08,580 --> 00:00:15,150 we've looked at lists and tuples and now we have yet another data type and these are 5 00:00:15,150 --> 00:00:23,430 dictionaries. Let me open the python shell. And let me create a list first I'm just 7 00:00:23,430 --> 00:00:28,140 creating this for reference, so to compare lists with dictionaries, but you 9 00:00:28,140 --> 00:00:32,940 don't need to create a list for creating a dictionary. So to create a dictionary 11 00:00:32,940 --> 00:00:40,140 you need curly brackets, so open and closing curly brackets and then inside 13 00:00:40,140 --> 00:00:45,719 that you'd pass the items of the dictionary. Now the difference here with 15 00:00:45,719 --> 00:00:52,230 dictionaries is that instead of letting Python add default indexes for your 17 00:00:52,230 --> 00:01:00,390 items you want to create those indexes yourself exclusively so therefore for 19 00:01:00,390 --> 00:01:09,960 dictionaries you do something like this. Name, a column and then the item. Let me 21 00:01:09,960 --> 00:01:20,159 write another one, surname column and then the other item and yeah that's it. 23 00:01:20,159 --> 00:01:25,950 That's the dictionary. So what we have here is when I was talking about 25 00:01:25,950 --> 00:01:31,229 indexing I was referring to these things. Actually these two are referred to as 27 00:01:31,229 --> 00:01:38,189 keys, not indexes so for dictionaries you can create custom indexes so to say and 29 00:01:38,189 --> 00:01:45,329 so these are keys so we have key and value, key and value. This is good because 31 00:01:45,329 --> 00:01:51,329 now if you want to access one of the values of the dictionary again you'd use 33 00:01:51,329 --> 00:01:56,939 square brackets just as you did with strings lists and tuples and then there you 35 00:01:56,939 --> 00:02:02,909 pass the key which value you want to extract, so if you want to extract John, 37 00:02:02,909 --> 00:02:09,300 you want to pass the key of John and that will extract the John value. Something 39 00:02:09,300 --> 00:02:13,470 to note is that dictionaries are an unordered colecton 41 00:02:13,470 --> 00:02:20,250 of items and so sometimes you may notice that the order of the key and 43 00:02:20,250 --> 00:02:26,550 values is not maintained so you may see that surname has gone to the first place, so 45 00:02:26,550 --> 00:02:32,160 surname Smith and the pair has gone the first one and name John is the second 47 00:02:32,160 --> 00:02:37,110 one and so on. So this is different from lists, strings and tuples. The reason why 49 00:02:37,110 --> 00:02:42,210 Python doesn't keep the order is that you know the way you access dictionaries 51 00:02:42,210 --> 00:02:49,890 is you exclusively pass the key of the dictionary when you access it and so you 53 00:02:49,890 --> 00:02:54,209 don't need to know the order of the dictionary. And whenever you want to access 55 00:02:54,209 --> 00:02:57,510 something you say the surname for instance and that will the return Smith 57 00:02:57,510 --> 00:03:02,340 no matter where Smith is, so whether it is the first one, the second one or over 59 00:03:02,340 --> 00:03:10,500 and so on. And interestingly in dictionaries you can also pass, you can 61 00:03:10,500 --> 00:03:17,940 have like lists as values or even tuples, so let me write a circle there or let me 63 00:03:17,940 --> 00:03:27,000 keep it like that and let me add another key and pair here. Let's say cities. Let's say 65 00:03:27,000 --> 00:03:42,750 Joe Smith lives in three cities, Porto and San Diego and Bali. You close 67 00:03:42,750 --> 00:03:49,769 bracket there so as you see we have the key here, we have a column and then you 69 00:03:49,769 --> 00:03:54,030 have the value which can be anything so it can be string, it can be a number, it 71 00:03:54,030 --> 00:04:01,100 can be at list, a tuple. In this case that's a tuple so if you access now 73 00:04:01,100 --> 00:04:10,070 cities like that, you'd get… Sorry, I'll add two bracket there, so you'd get the tuple. 75 00:04:10,070 --> 00:04:15,959 And then you can also do tricks like you know if you want to access Bali you'd 77 00:04:15,959 --> 00:04:23,789 have other brackets there and pass 2. And that would return Bali, so why is that? 79 00:04:23,789 --> 00:04:27,710 That's because you know up to here you have a tuple, 81 00:04:27,710 --> 00:04:35,849 but that's a triple object and then from that tuple you use again the 83 00:04:35,849 --> 00:04:40,560 square brackets notation to access an item from that tuple, so you want item 85 00:04:40,560 --> 00:04:47,759 with index two and that is Bali and yeah that's about dictionaries. Try them out 87 00:04:47,759 --> 00:04:55,110 some more, play around and you will be able to comfortably create and access items 89 00:04:55,110 --> 00:05:01,099 from a dictionary. So I hope you enjoyed this and talk to you later.

1 00:00:00,350 --> 00:00:05,279 Let's now look at tuples. In the previous lecture we looked at lists and 3 00:00:05,279 --> 00:00:10,790 tuples are very similar to lists, the only difference is that tuples are not 5 00:00:10,790 --> 00:00:17,520 mutable, so you cannot change a tuple. Lists are used much more than tuples 7 00:00:17,520 --> 00:00:24,269 so tuples are only using very specific scenarios, so we will see some scenarios 9 00:00:24,269 --> 00:00:28,109 throughout the course when we build the real-world applications, so you don't 11 00:00:28,109 --> 00:00:32,430 have to worry about understanding when to use a tuple in programming for now. 13 00:00:32,430 --> 00:00:41,640 Anyway I want to show you the syntax, so you can create a tuple like that. 15 00:00:41,640 --> 00:00:48,800 So tuples just like lists, they contain they may contain different data types. 17 00:00:48,800 --> 00:00:56,340 Let's say 3 4 and so on. Oh sorry, I was writing in the 19 00:00:56,340 --> 00:01:04,700 terminal, let me open the Python shell so again 21 00:01:04,700 --> 00:01:11,850 we have strings numbers and floats if you like. Whatever type that you want you can pass 23 00:01:11,850 --> 00:01:17,150 in a tuple and in a list and of course you can use indexing for tuples as well, 25 00:01:17,150 --> 00:01:25,799 so let's access the lost item and that will give 4.6. The difference is that you 27 00:01:25,799 --> 00:01:32,520 know tuples they have some slight different methods than lists, so if you 29 00:01:32,520 --> 00:01:39,600 dir list, you see that lists have much more methods available than tuples, 31 00:01:39,600 --> 00:01:46,890 so for instance you can append items to a list, you can clear the list and copy 33 00:01:46,890 --> 00:01:54,149 and count, count is available for tuples because count doesn't change the data type, 35 00:01:54,149 --> 00:01:58,829 so it doesn't change the tuple, it just counts how many items are there in the tuple. 37 00:01:58,829 --> 00:02:04,259 As I said, tuples are immutable, so you cannot change them that's why these 39 00:02:04,259 --> 00:02:09,959 methods that change the data type like inserting new values and popping out 41 00:02:09,959 --> 00:02:14,280 values, removing values, reversing and sorting so these 43 00:02:14,280 --> 00:02:19,590 are not available and yeah this is more or less about tuples. In case you need them 45 00:02:19,590 --> 00:02:26,840 later they are there for you. Hope you're enjoying the course and I'll talk to you later.

1 00:00:01,550 --> 00:00:08,189 Great, now let's look at lists, so in the previous lecture we were looking at 3 00:00:08,189 --> 00:00:14,250 strings and indexing and splitting strings and I will be working with lists 5 00:00:14,250 --> 00:00:20,210 which are very similar to strings. They are similar because they are both 7 00:00:20,210 --> 00:00:25,949 referred to as sequences, so there are sequences of items. The difference is 9 00:00:25,949 --> 00:00:35,910 that, let me open Python, and so the difference is that the string is made of 11 00:00:35,910 --> 00:00:41,730 other strings so it can contain only strings of characters or strings. 13 00:00:41,730 --> 00:00:49,079 whatever you like to call it, however lists can contain various other data 15 00:00:49,079 --> 00:01:00,809 types, let's say H a letter, a number, and also a string. So this is a string the 17 00:01:00,809 --> 00:01:05,970 first one, this is a number, an integer. This is also string with multiple 19 00:01:05,970 --> 00:01:14,460 characters and that is a list, so for this you want to use square brackets to 21 00:01:14,460 --> 00:01:21,450 create a list. Execute and yeah you can call it and so this is a list of three 23 00:01:21,450 --> 00:01:26,460 items and you can also store other objects in a list but we'll cover other 25 00:01:26,460 --> 00:01:33,320 objects in later sections, you know we have table of objects with lots of data. 27 00:01:33,320 --> 00:01:39,180 You may store files in a list you may store widgets of a graphical user 29 00:01:39,180 --> 00:01:45,570 interface that you are building and so on, so these are very useful and lists also 31 00:01:45,570 --> 00:01:51,180 have indexing and you can split lists, you can extract items and so on. So the 33 00:01:51,180 --> 00:01:56,790 good news is that lists have the same indexing system as strings and so 35 00:01:56,790 --> 00:01:59,790 you've learned that in the previous lecture and you can go ahead and apply 37 00:01:59,790 --> 00:02:06,979 that system not, so let's extract number 2. That would have an index of one. 39 00:02:06,979 --> 00:02:14,720 Execute that and yeah you get 2 there. If you check the type you'll see that's an integer. 41 00:02:14,720 --> 00:02:20,760 So every item of a list has its own data type, even also access more than 43 00:02:20,760 --> 00:02:28,970 white one item of a list. Let's say you want the first two items. You do 0 1 2, so 45 00:02:28,970 --> 00:02:38,010 like that or 0 to 2 whatever you like. That will produce another list so the 47 00:02:38,010 --> 00:02:49,459 type of this split is a list. The type of the split of a string is a string, so S 49 00:02:49,459 --> 00:02:57,390 for the string here, C for the list. Lists now have methods associated with 51 00:02:57,390 --> 00:03:02,130 them just like strings do and so you can check what methods you have available 53 00:03:02,130 --> 00:03:08,220 there by just doing a dir list. So this a the blueprint you can use 55 00:03:08,220 --> 00:03:13,200 lists, you can pass empty square brackets in there, it's the same thing and then 57 00:03:13,200 --> 00:03:20,510 you can use help to look at each of these methods, so these are the methods. 59 00:03:20,510 --> 00:03:31,260 Without the underscore and let's look at the append method, so to apply methode 61 00:03:31,260 --> 00:03:39,690 you do c the dot notation append and here on that 3. What that does, it adds 63 00:03:39,690 --> 00:03:44,549 another item to the end of the list, So it appends an item to the 65 00:03:44,549 --> 00:03:49,850 list and you can explore the other methods if you like so let's say help. 67 00:03:49,850 --> 00:03:59,160 Remove like that and you'll see how to use that remove method, so you do 69 00:03:59,160 --> 00:04:03,750 c.remove and then you pass the value of the item that you want to remove, so 71 00:04:03,750 --> 00:04:10,440 not the index but the value. Let's say we want to remove 2 and you see that 2 73 00:04:10,440 --> 00:04:16,979 is now gone from the list so look at the other methods of the list and try 75 00:04:16,979 --> 00:04:21,720 to experiment with this and play around with them access items and split them 77 00:04:21,720 --> 00:04:27,470 and you'll be good to go then. Thanks, I'll talk to you later.

1 00:00:00,030 --> 00:00:04,290 Hi again, in the previous lecture we talked about strings and in this lecture 3 00:00:04,290 --> 00:00:10,500 again we are going deeper into learning strings and specifically we're going to add 5 00:00:10,500 --> 00:00:16,260 indexing. Indexing is a very important concept not only with strings but 7 00:00:16,260 --> 00:00:21,150 with all the data type that we'll be looking at later such as lists, 9 00:00:21,150 --> 00:00:26,880 tuples and dictionaries, so please follow this lecture. Yeah, let's talk about 11 00:00:26,880 --> 00:00:35,070 indexing. Let me open the Python interactive session. Let me create a 13 00:00:35,070 --> 00:00:44,070 string, "Hi there!" exclamation mark and close quote. 15 00:00:44,070 --> 00:00:48,989 Now when you create a string, every string that you create Python under the hood 17 00:00:48,989 --> 00:00:57,930 what it does is it assigns a number to each or the items of your string so it 19 00:00:57,930 --> 00:01:06,780 starts from 0 so H will be assigned an index of 0 and then a 1 for I, 2 for the 21 00:01:06,780 --> 00:01:12,799 space, 3 for T, five, six seven, eight. 23 00:01:12,799 --> 00:01:18,990 So the exclamation mark character will will have an index of eight, so you would 25 00:01:18,990 --> 00:01:26,360 ask why is this useful? Well this allows you to extract certain parts from a 27 00:01:26,360 --> 00:01:33,600 string and there is a certain notation to do that you'd want to access the string. 29 00:01:33,600 --> 00:01:39,270 So in this case that's variable C holding the string, then you want to use 31 00:01:39,270 --> 00:01:44,579 square brackets so an opening square bracket and then a closing square 33 00:01:44,579 --> 00:01:49,350 bracket and inside those square brackets you pass the index of the item that you want 35 00:01:49,350 --> 00:01:58,170 to extract. Let's say I want the T character so that would be 0 1 2 3. 37 00:01:58,170 --> 00:02:05,490 I pass number 3 there as an index and that will extract for me the letter T which is 39 00:02:05,490 --> 00:02:10,800 actually a string. So you can check the type of the 41 00:02:10,800 --> 00:02:15,810 output and you'll see that that's a string, so a string is made of strings. 43 00:02:15,810 --> 00:02:22,950 You can say so. If you wanted H you'd past zero and if you wanted a lost 45 00:02:22,950 --> 00:02:28,260 character well you might have to count so one two three four five six seven 47 00:02:28,260 --> 00:02:33,330 eight. And so, and sorry including type there. 49 00:02:33,330 --> 00:02:38,880 Sorry about that! so c8 would give you the exclamation 51 00:02:38,880 --> 00:02:45,720 mark, but there's also another indexing system there that Python uses so in this 53 00:02:45,720 --> 00:02:50,519 case we had to count from the beginning to the end of the string but wouldn't it 55 00:02:50,519 --> 00:02:56,370 be useful if you had another system that lets you count from the end, so from 57 00:02:56,370 --> 00:03:00,780 right to left? Well, such a system exists and it 59 00:03:00,780 --> 00:03:08,400 starts from minus 1, so the exclamation mark would be minus 1 now that you can 61 00:03:08,400 --> 00:03:18,989 extract that with that. Minus 2 would be E, R would be minus 3 and so on up to H, so we 63 00:03:18,989 --> 00:03:25,019 have two indexing systems there which allow you to extract items depending on 65 00:03:25,019 --> 00:03:30,090 whether the items are in the beginning or near the end. Now what if you want to 67 00:03:30,090 --> 00:03:36,959 extract more than one item from a string? Let's say you want to extract Hi. 69 00:03:36,959 --> 00:03:47,090 Well there is a notation for that too, so Hi is expanding from index 0 to index 1. 71 00:03:47,090 --> 00:03:57,380 So up to here. So let's try 0 to 1. That will not work a very good, but let's see. 73 00:03:57,380 --> 00:04:05,130 So as I said this will return only H, so it doesn't return item with index 1. 75 00:04:05,130 --> 00:04:11,250 That's because splitting in Python, so we we're splitting a string here 77 00:04:11,250 --> 00:04:17,609 splitting in Python is upper bound exclusive, which means that the upper 79 00:04:17,609 --> 00:04:24,730 bounds of the split here is not included in the output and so if you want to 81 00:04:24,730 --> 00:04:33,070 include I you want to pass the index after I which is two so this is the string 83 00:04:33,070 --> 00:04:40,420 just for reference, so we extracted item with index 0 and item with index 1. 85 00:04:40,420 --> 00:04:46,770 And then the split starts right there at index 2 so it doesn't include the space. 87 00:04:46,770 --> 00:04:54,430 Just hi. If you pass 3 there, that would include the wide space as well and 89 00:04:54,430 --> 00:05:00,310 similarly you can pass like one. That will include the I and the space, there 91 00:05:00,310 --> 00:05:06,970 are also shortcuts, so if you pass zero like nothing to 3 but that is the same 93 00:05:06,970 --> 00:05:18,120 as doing 0 to 3 so it will include 0 1 & 2 and similarly if you want to extract 95 00:05:18,120 --> 00:05:24,760 there with the exclamation mark well what you'd want to do is T would 97 00:05:24,760 --> 00:05:32,919 have an index of 0 1 2 3 so 3 and then you can just pass a column there and 99 00:05:32,919 --> 00:05:38,830 execute it and that will give you There with the exclamation mark. Let's now try 101 00:05:38,830 --> 00:05:46,240 to extract R and E using negative indexing, so something to know is that 103 00:05:46,240 --> 00:05:50,200 even though we are using a negative indexing which starts from right to left 105 00:05:50,200 --> 00:05:56,530 the splitting will work from left to right which means the first index you 107 00:05:56,530 --> 00:06:05,140 want to pass is that of the first item. So R we pass minus 3 for R because 109 00:06:05,140 --> 00:06:15,300 you know we have minus 1, minus 2 and minus 3. So minus 3 for R and then we want E 111 00:06:15,300 --> 00:06:21,450 which is minus 2, but since splitting is upper bounce 113 00:06:21,450 --> 00:06:30,430 exclusive we want to pass minus one there. So let's try that, minus one, execute and yeah 115 00:06:30,430 --> 00:06:35,360 we get the correct output. That's the idea. If you didn't pass 117 00:06:35,360 --> 00:06:40,640 anything here you'd get the exclamation mark as well. So it will take a while 119 00:06:40,640 --> 00:06:45,050 until we get used to this, but with some practice you'll be able to remember 121 00:06:45,050 --> 00:06:52,010 these notations. Yeah, that's what I wanted to cover in this lecture, so this was 123 00:06:52,010 --> 00:06:58,100 about string indexing and splitting, so you split using the index that Python 125 00:06:58,100 --> 00:07:02,660 uses on the background. Yeah, I hope you enjoyed this and I'll talk to you 127 00:07:02,660 --> 00:07:05,470 later, thanks!

1 00:00:00,030 --> 00:00:05,240 Hi, welcome again. In the previous lecture we were talking about numbers. 3 00:00:05,240 --> 00:00:11,370 Specifically we looked at integers and float data types so these are referred 5 00:00:11,370 --> 00:00:15,809 to as data types in Python, so integers and floats. In this lecture we're going 7 00:00:15,809 --> 00:00:23,970 to look at strings. I already mentioned strings in the previous lecture. 9 00:00:23,970 --> 00:00:30,410 So a string is everything that goes inside quotes. "Hi there". That is a string. 11 00:00:30,410 --> 00:00:40,170 And of course strings can be stored in variables and you can print those 13 00:00:40,170 --> 00:00:44,579 variables, so we're using the interactive shell now, but of course you can use a 15 00:00:44,579 --> 00:00:51,899 part of script as we did previously. So numbers were used to do math operations, 17 00:00:51,899 --> 00:00:58,070 but strings, strings are used for displaying information for the user. 19 00:00:58,070 --> 00:01:04,320 So let's say you have a web application, and you want to generate some text 21 00:01:04,320 --> 00:01:10,140 dynamically on the web page, so you'd use would use Python on the backend and 23 00:01:10,140 --> 00:01:18,509 Python would send strings to the HTML code and HTML would render the 25 00:01:18,509 --> 00:01:24,689 code on the web page basically that's the idea or if you want to create a 27 00:01:24,689 --> 00:01:31,229 notepad, an editor with Python such as Atom let's say, all these things you see 29 00:01:31,229 --> 00:01:37,170 here so my program.py selection file, so all this would be written as 31 00:01:37,170 --> 00:01:43,710 strings inside Python and then you display them on the interface using 33 00:01:43,710 --> 00:01:48,780 various functions, for instance if you want to display a string on the terminal 35 00:01:48,780 --> 00:01:57,030 you'd use the print function. Now strings have methods associated with them. What I 37 00:01:57,030 --> 00:02:04,079 mean with methods is let me go ahead and try out a method. Methods, for 39 00:02:04,079 --> 00:02:10,860 methods you need to use the dot notation. So you'd refer to the string which is 41 00:02:10,860 --> 00:02:15,760 string c in our case actually variable c, but the variable is holding 43 00:02:15,760 --> 00:02:24,750 the strings so it's the same as doing here dot, so let's do c dot, replace and 45 00:02:24,750 --> 00:02:33,910 what I want to replace is e with i. So I'm replacing, for string here I'm 47 00:02:33,910 --> 00:02:42,310 replacing letter e with later i and what that will do it will replace all 49 00:02:42,310 --> 00:02:50,620 the letters, all the occurrences of this letter in the string, so you'd ask where 51 00:02:50,620 --> 00:02:55,739 can we see these method? Well that's very easy actually. You can do dir and 53 00:02:55,739 --> 00:03:01,540 then pass the string there, any string. It could be c, it could be an empty string 55 00:03:01,540 --> 00:03:07,930 or whatever and that will print out all the available methods that you can use 57 00:03:07,930 --> 00:03:16,630 with strings, so let's say c dot upper. That will cover the strings to 59 00:03:16,630 --> 00:03:22,630 upper case letters. Now if you want to know what these methods are about you 61 00:03:22,630 --> 00:03:29,380 could ask for help. Just do help and then c, so the 63 00:03:29,380 --> 00:03:40,810 string or just empty string dot 65 00:03:44,320 --> 00:03:52,450 here replace method of the string instance, so string is like the blueprint 67 00:03:52,450 --> 00:03:58,560 that creates strings objects or you can say the data type that represents texts. 69 00:03:58,560 --> 00:04:08,950 Look here. Here is the syntax, so what you do is, you use a string like we did. 71 00:04:08,950 --> 00:04:16,840 So let's say here replace. Then you open brackets. Here is the old item you want 73 00:04:16,840 --> 00:04:24,490 to remove from the string and then the new item we want to replace it with i and 75 00:04:24,490 --> 00:04:30,140 then what you see here in square brackets, that means this parameter is 77 00:04:30,140 --> 00:04:35,330 optional so you can either pass it or not and you know in the previous case we 79 00:04:35,330 --> 00:04:42,100 didn't pass it so what Python did was it replaced all the occurrences of the i 81 00:04:42,100 --> 00:04:48,070 item but if you want to replace only the first occurrence you do one there and 83 00:04:48,070 --> 00:04:54,770 that will replace all the first i over the first e with i. That's how it works 85 00:04:54,770 --> 00:05:02,720 So strings, they support functions, so print is a function. Here. And they support 87 00:05:02,720 --> 00:05:08,530 methods like this one here and they also support operators so you get "Here" 89 00:05:08,530 --> 00:05:19,190 plus "There" and you get "HereThere" or you can make it more readable like that so 91 00:05:19,190 --> 00:05:23,930 an empty space is also a string and yeah that's about strings for now and I'll 93 00:05:23,930 --> 00:05:26,380 talk to you later.

1 00:00:00,269 --> 00:00:04,680 Hi again, in this lecture I'll show you how to do math operations with numbers. 3 00:00:04,680 --> 00:00:10,200 So we're going to look at math operators. Let's go straight away and open a Python 5 00:00:10,200 --> 00:00:16,880 section and let me write a math expression there. 20 minus 10 divided by 7 00:00:16,880 --> 00:00:31,019 5 times 3 in the power of 2 and what we get is 2.0. So why did I write this a 9 00:00:31,019 --> 00:00:36,239 long expression? Well because I want to explain to you the order of operators so 11 00:00:36,239 --> 00:00:41,760 when you have multiple operators in an expression the one to be executed 13 00:00:41,760 --> 00:00:50,910 first is the exponent, so we have 3 in power of 2 here that will give us 9. 15 00:00:50,910 --> 00:00:56,120 So power is the first to be executed and also that is division and multiplication. 17 00:00:56,120 --> 00:01:00,210 Actually division and multiplication are on the same level. 19 00:01:00,210 --> 00:01:06,330 We're talking about order but the one that is first will be executed first so in 21 00:01:06,330 --> 00:01:11,640 this case division is the first one so what will happen here is Python will 23 00:01:11,640 --> 00:01:16,500 ignore minus for now, so it will divide 10 by 5 and it will 25 00:01:16,500 --> 00:01:30,180 give 2 then it will do 2 times 9. So again 10 divided by 5, 2 times 9, 19. 27 00:01:30,180 --> 00:01:35,220 And then we have the rest of the operators which could be a plus or minus so in 29 00:01:35,220 --> 00:01:45,299 this case we have minus so 20 minus 18. We have 2.0. You'd ask why we have 2.0? 31 00:01:45,299 --> 00:01:54,509 Because 10 divided by 5 gives 2.0. So division outputs a float in Python 3. 33 00:01:54,509 --> 00:02:00,540 If you are on Python 2, it would output an integer. Now to make your expressions 35 00:02:00,540 --> 00:02:10,590 look better, you'd want to remove the spaces for the power operator and also 37 00:02:10,590 --> 00:02:15,569 you do like that somehow you can read it better, 39 00:02:15,569 --> 00:02:23,550 so 2 times 9 and then 20 minus 18 and so on. You get the idea. 41 00:02:23,550 --> 00:02:33,599 You get 2.0 again and now if you want to execute the minus operator first 43 00:02:33,599 --> 00:02:38,569 you'd want to put that inside brackets. So why did we get 18? Well because 20 45 00:02:43,890 --> 00:02:52,940 minus 10 gives 10 and then 10 divided by 5 gives 2 and then 2 times 9 gives 18. 47 00:02:52,940 --> 00:03:02,459 That's the idea. And then you could also do this, put these in brackets and what 49 00:03:02,459 --> 00:03:13,890 would happen here is you know 10 here, 15 here in the power of 2, so 15 in the 51 00:03:13,890 --> 00:03:20,459 power of 2, and then 10, so 10 divided by 15 in the power of 2. Let's see what we get. 53 00:03:20,459 --> 00:03:25,920 Yeah we got that, so let's see if I was 55 00:03:25,920 --> 00:03:31,260 Right. 15 in the power of 2 we get 225. 57 00:03:31,260 --> 00:03:42,510 And then we got 10 on the other side, so 10 divided by 225. We get that number. 59 00:03:42,510 --> 00:03:46,349 So whenever you want to change the order of operators, you should use 61 00:03:46,349 --> 00:03:53,549 brackets and so I hope you get the idea and please try this out, so try to do a 63 00:03:53,549 --> 00:03:57,569 few operations with numbers to get used to it. And yeah, I'll talk to you later. 65 00:03:57,569 --> 00:04:00,379 Thanks.

1 00:00:00,469 --> 00:00:07,770 Great, now let's learn numbers. Let me open an interactive shell here to 3 00:00:07,770 --> 00:00:13,380 explain this faster and so numbers, you know what numbers are. To create a number 5 00:00:13,380 --> 00:00:19,640 just type the number in python and that's it and you also have operators 7 00:00:19,640 --> 00:00:25,350 like this is the plus operator and you can also store numbers in variables 9 00:00:25,350 --> 00:00:33,020 let's say a equals to 2, b equals to 3 and then if you do a plus b you get 5. 11 00:00:33,020 --> 00:00:41,550 Something to note is that you know if you do that in here, a equals to 2 b 13 00:00:41,550 --> 00:00:48,170 equals to 3, and then if you just do a plus B and then you execute the script, 15 00:00:48,170 --> 00:00:58,739 let me open another terminal, you will not get any output in there. The reason 17 00:00:58,739 --> 00:01:04,559 is that you are not printing out anything in your program, so this is 19 00:01:04,559 --> 00:01:10,229 different from an interactive session. Here if you simply do an operation or if 21 00:01:10,229 --> 00:01:16,650 you simply call a variable like that, you'll get the output promptly, so this is just 23 00:01:16,650 --> 00:01:21,840 for simplicity when you when you try things out, so you don't have to pass 25 00:01:21,840 --> 00:01:27,600 print explicitly, but Python will understand that you met print. But here 27 00:01:27,600 --> 00:01:35,130 things are more strict, so you if you want to print out the output, you want 29 00:01:35,130 --> 00:01:43,680 to say print a plus b and then execute and you get the output and yeah basically 31 00:01:43,680 --> 00:01:48,960 that's the only difference between executing a program from a Python file 33 00:01:48,960 --> 00:01:56,130 and running the code in the interactive shell, so these are numbers and I can 35 00:01:56,130 --> 00:02:03,439 prove that if I do type 2 for instance. You'll see that this is an INT 37 00:02:03,439 --> 00:02:10,289 type which means is an integer, so basically we have integers and we have 39 00:02:10,289 --> 00:02:13,799 floats. These are the two main types of numbers. 41 00:02:13,799 --> 00:02:22,379 A float is, let's say 2.4 it's a float and I can prove that 2.4, 43 00:02:22,379 --> 00:02:30,359 type 2.4. You'll see that this is a float, however if you do type 2 in 45 00:02:30,359 --> 00:02:35,609 brackets you'll see that this is a string, it's not a number and therefore 47 00:02:35,609 --> 00:02:42,689 you cannot make operations using a string and a number so Python will give 49 00:02:42,689 --> 00:02:47,430 you a type error and this is saying cannot convert integer to string 51 00:02:47,430 --> 00:02:54,569 implicitly so when you do a string plus something else Python expects that you 53 00:02:54,569 --> 00:03:00,000 were adding another string after a plus sign, so that's why it says I cannot 55 00:03:00,000 --> 00:03:05,549 convert integer object, so it cannot convert this to a string implicitly 57 00:03:05,549 --> 00:03:14,040 because if you were to do two plus three you'd get 23 because Python treats these 59 00:03:14,040 --> 00:03:17,189 two as text. So to understand it better 61 00:03:17,189 --> 00:03:26,729 let's add some text here b so you get 2a3b, so it's a concatenation operation. 63 00:03:26,729 --> 00:03:31,199 When the plus operator is used with strings it is referred to as 65 00:03:31,199 --> 00:03:37,010 concatenation. Now let's go back to our sample program that we used earlier 67 00:03:37,010 --> 00:03:44,549 which was this one in here, so now what if instead of getting a greeting from 69 00:03:44,549 --> 00:03:53,220 the user you ask their for their age? Enter your age, so this is just a message 71 00:03:53,220 --> 00:03:56,879 you can write anything you want there, but just try to have a message that 73 00:03:56,879 --> 00:04:04,680 makes some sense to the user and so also I'm going to change the variable name to 75 00:04:04,680 --> 00:04:11,400 something more meaningful, age and then what I want to do is let's say new age, 77 00:04:11,400 --> 00:04:18,790 I want to calculate the age plus 50. Why not? 79 00:04:18,790 --> 00:04:28,540 I'll print out the new age. Save the script and let's go and execute this, we are 81 00:04:28,540 --> 00:04:33,130 going to get an error here I warn you. But it's good that you see the errors 83 00:04:33,130 --> 00:04:36,030 that you get because that's how you learn better. 85 00:04:36,030 --> 00:04:45,580 So Python my program, execute. For now it's working fine because what 87 00:04:45,580 --> 00:04:51,280 happens is Python executes a script line by line so it goes to the first 89 00:04:51,280 --> 00:04:56,980 line and if there is no error it executes that line and in this case we have 91 00:04:56,980 --> 00:05:02,830 an input function so the program is on standby mode so it expects from the user 93 00:05:02,830 --> 00:05:10,780 to enter the input, so let's enter the input here. Let's say 28 and here is the 95 00:05:10,780 --> 00:05:16,420 error that we get. So again we saw this error before. This is saying type error 97 00:05:16,420 --> 00:05:21,250 cannot convert int object to string implicitly and you also have the line 99 00:05:21,250 --> 00:05:30,630 here that the error occurred. So these are important messages and line two in here. 101 00:05:30,630 --> 00:05:37,270 So what's happening is that age is a string it's not a number therefore 103 00:05:37,270 --> 00:05:43,180 python cannot add up a string with a number and so why is age a string? 105 00:05:43,180 --> 00:05:48,520 Because that's what the input function produces, so the input function get the 107 00:05:48,520 --> 00:05:55,000 user input and converts it to a string so even if you pass a number there these 109 00:05:55,000 --> 00:05:59,140 will always convert everything to a string. 111 00:05:59,140 --> 00:06:07,570 Therefore Python you know cannot concatenate 28 plus 50 so what can you 113 00:06:07,570 --> 00:06:13,480 do in that case? Well you want to convert that string into an integer and for 115 00:06:13,480 --> 00:06:19,360 that you want to use the int function, so it's a Python function that does the work. 117 00:06:19,360 --> 00:06:27,570 As you can see it outputs now the correct output so 28 plus 50 equals 119 00:06:27,570 --> 00:06:32,410 78 and similarly you can convert numbers to strings 121 00:06:32,410 --> 00:06:42,280 and let's say str 50 and I think we'll get an error here. Yeah, it says type error. 123 00:06:42,280 --> 00:06:48,580 Unsupported operand type four plus. So you're adding up an integer with a 125 00:06:48,580 --> 00:06:57,850 string, so integer with a string. If you like to convert this to a float, let me 127 00:06:57,850 --> 00:07:07,270 remove that, save, execute. 28. You get 78 point zero because what 129 00:07:07,270 --> 00:07:19,330 Python does when you use float is you know float 28, it converts it to 28.0. 131 00:07:19,330 --> 00:07:24,160 So floats can be useful in certain scenarios. And you'll have a lot of scenarios in the 133 00:07:24,160 --> 00:07:28,690 course, so don't worry about that now because we have real world 135 00:07:28,690 --> 00:07:33,490 applications later on where you see the real benefit of everything that you are 137 00:07:33,490 --> 00:07:39,040 explaining here in this early sections that cover the basics. So this is about 139 00:07:39,040 --> 00:07:43,540 numbers. Try to practice them a little bit and I'll talk to you in the next 141 00:07:43,540 --> 00:07:45,690 lecture.

1 00:00:00,210 --> 00:00:05,400 Hi, in this lecture you're going to learn about variables. So what is a variable? 3 00:00:05,400 --> 00:00:10,980 Well a variable is like a container where you can store various data types 5 00:00:10,980 --> 00:00:18,539 in Python for instance this program now this doesn't have any variable in it for 7 00:00:18,539 --> 00:00:23,699 now, so let me try and execute it and you'll see that this prints out of the 9 00:00:23,699 --> 00:00:29,609 hello string. String is a data type, but we'll cover that later. Now what is the 11 00:00:29,609 --> 00:00:38,790 variable? Well and variables will keep your code more organized. Let me create a 13 00:00:38,790 --> 00:00:45,149 variable here, greeting so you can call your variables whatever you like you can 15 00:00:45,149 --> 00:00:50,070 give them any name however there are some naming rules which I'll mention in 17 00:00:50,070 --> 00:00:55,739 just a bit, so let me create this variable for now. I'll store in this 19 00:00:55,739 --> 00:01:01,980 variable, I said variables are like containers so I'll store this text in the 21 00:01:01,980 --> 00:01:07,799 variable greeting and then what I do is instead of doing print hello I'll do 23 00:01:07,799 --> 00:01:15,570 print greeting and save the script ctrl s and then go through the command line, 25 00:01:15,570 --> 00:01:22,229 the upper arrow key, enter to execute and you get the same output. So this is how 27 00:01:22,229 --> 00:01:26,670 you create a variable you don't use any quotes because when you use quotes you 29 00:01:26,670 --> 00:01:34,229 are creating a string data type not a variable and you can also use a dash 31 00:01:34,229 --> 00:01:43,439 before the variable that would also be fine so you get the output correctly 33 00:01:43,439 --> 00:01:50,549 but you cannot use numbers before the variable ctrl s to save, execute and get 35 00:01:50,549 --> 00:01:56,820 an invalid syntax, so this syntax is not valid in Python, but you can use numbers 37 00:01:56,820 --> 00:02:09,119 after or between the variable name let's say here greeting2. So that would 39 00:02:09,119 --> 00:02:13,860 be fine to use so that's the condition about naming 41 00:02:13,860 --> 00:02:19,470 your variables, you can start them with a letter or a, or an underscore. Now if 43 00:02:19,470 --> 00:02:24,720 you're not experienced with programming you may still be confused on why do we 45 00:02:24,720 --> 00:02:31,370 use these variables? Well this is a very simple program, actually very useless, but 47 00:02:31,370 --> 00:02:37,140 normally your programs will interact with your users. That is what we call a 49 00:02:37,140 --> 00:02:43,140 real program. You create a program to give it to people so they can interact 51 00:02:43,140 --> 00:02:48,810 with the program they can generate all different outputs and so on, so let's go 53 00:02:48,810 --> 00:02:57,060 Ahead and make this program more dynamic, so what I'll do here is I'll get the text 55 00:02:57,060 --> 00:03:03,720 from the user interactively. To do that you need to use the input function, this 57 00:03:03,720 --> 00:03:09,959 is also a Python function and inside the function you can enter a message to the 59 00:03:09,959 --> 00:03:16,640 user so let's say write a greeting. A column and make some space there and then 61 00:03:20,519 --> 00:03:28,290 you print greeting2, save the script. Execute and now the program is asking 63 00:03:28,290 --> 00:03:36,060 us to enter some input so let's go ahead and say hi this time and we get the output 65 00:03:36,060 --> 00:03:42,150 Printed out in here, hi, so what happened here is we created a variable 67 00:03:42,150 --> 00:03:49,320 and that variable will store the value that the user submits in the command line 69 00:03:49,320 --> 00:03:55,590 here, in the terminal so the user submitted the hi text and this text will be 71 00:03:55,590 --> 00:04:00,989 stored in this variable so as I said variables are like containers and then can 73 00:04:00,989 --> 00:04:06,390 use this text in various ways, but in this scenario I'm just passing it to the 75 00:04:06,390 --> 00:04:12,030 print function, so I want to print it out on the terminal here and the print 77 00:04:12,030 --> 00:04:16,709 function will get the value that is stored in the greeting2 variable and 79 00:04:16,709 --> 00:04:22,650 print it out on the terminal. That's it. And yeah, I'd like to close this lecture 81 00:04:22,650 --> 00:04:27,110 now and I'll see you in the next lecture.

External Link:~ https://www.windowscentral.com/how-add-open-command-prompt-window-here-back-context-menu-windows-10 Frequently Asked Questions: file:///C:/Users/Taha%20Umar%20Farooq/Videos/FOLDER/[Tutsgalaxy.com]%20-%20The%20Python%20Mega%20Course%20Build%2010%20Real%20World%20Applications/01%20Getting%20Started/009%20Installation%20FAQs.html 1 00:00:00,000 --> 00:00:06,870 Hello again. This is yet another lecture for Mac users and in this s lecture I'm going 3 00:00:06,870 --> 00:00:12,389 to show you how to set up for the Atom editor on a Mac computer so if you're a 5 00:00:12,389 --> 00:00:19,439 Windows user please skip this lecture. Atom is quite an advanced editor but if 7 00:00:19,439 --> 00:00:25,230 you have your favorite editor by now you can go ahead and use that editor so 9 00:00:25,230 --> 00:00:32,009 that's perfectly fine. If you choose to Look, to have a look at the Atom editor 11 00:00:32,009 --> 00:00:38,100 then please follow this lecture. First of all you're going to have to 13 00:00:38,100 --> 00:00:50,879 download Atom. Simply search for Atom editor and then go to its website which 15 00:00:50,879 --> 00:01:01,500 Atom.io, download for Mac and so while you wait for the download this 17 00:01:01,500 --> 00:01:09,360 is how the Atom editor will look like so like that and so the download has finished 19 00:01:09,360 --> 00:01:25,680 on my end and you can go and click Atom. Click open and basically Atom 21 00:01:25,680 --> 00:01:31,680 has been downloaded and has been installed so you've got a welcome guide 23 00:01:31,680 --> 00:01:41,280 in here, you can close that. This is an empty file. I'm going to close it as 25 00:01:41,280 --> 00:01:51,090 well and let me close Atom and try to show you how to actually open it from 27 00:01:51,090 --> 00:01:56,700 Scratch, so how to start Adam from the beginning and so let's see how to create 29 00:01:56,700 --> 00:02:03,390 a program and execute a program with Atom and now you want to launch Atom 31 00:02:03,390 --> 00:02:10,369 and then go to view, developer open in dev mode and that 33 00:02:15,319 --> 00:02:20,209 will ask you for the directory that you want to open, so go to the desktop, go to 35 00:02:20,209 --> 00:02:24,620 the folder where you have your programs or the folder where you want to create 37 00:02:24,620 --> 00:02:35,209 your programs if you haven't created any program yet and click open. 39 00:02:35,209 --> 00:02:44,510 And so you get this tree view in here and close that and double-clicking a file will open the 41 00:02:44,510 --> 00:02:51,109 file here in the editor and so you can go ahead and add more code there. 43 00:02:51,109 --> 00:02:59,030 Three plus four, you can also create other files, so you right click on 45 00:02:59,030 --> 00:03:11,750 the main directory, go to new file, Myprogram2.py. Let's say print 47 00:03:11,750 --> 00:03:19,849 five this time and ctrl s to save and so you have two programs now in here and you 49 00:03:19,849 --> 00:03:26,510 can switch through different files by clicking the tabs in here. So how to 51 00:03:26,510 --> 00:03:31,669 execute this programs now? Well you can use your Mac terminal just as you did in 53 00:03:31,669 --> 00:03:36,470 the previous lecture or even better you can go ahead and install a 55 00:03:36,470 --> 00:03:49,890 package, so go two packages settings view, open, go to install. 57 00:03:49,890 --> 00:04:10,860 Type platformio ide, so dash ide dash terminal. Enter to search and then go 59 00:04:10,860 --> 00:04:17,459 ahead and install the platformio ide 61 00:04:20,760 --> 00:04:25,200 platformio ide terminal has been installed successfully, so you can go ahead 63 00:04:25,200 --> 00:04:32,370 and close settings and you'll see a plus icon in here. If you click that 65 00:04:32,370 --> 00:04:43,230 an embedded terminal will open in Atom editor and you can drag it down and up 67 00:04:43,230 --> 00:04:52,650 to resize it. If you see closely you'll notice that the terminal is open in the 69 00:04:52,650 --> 00:05:00,150 current folder, see so untitled folder this one in here and that means you can go 71 00:05:00,150 --> 00:05:07,290 ahead and use Python now, Python 3 and execute a program, my program, my temp 73 00:05:07,290 --> 00:05:17,550 program.py and that will print hello. Actually it was supposed to print 75 00:05:17,550 --> 00:05:24,120 hello and then 7 but maybe I didn't save the script, so click on the editor 77 00:05:24,120 --> 00:05:31,890 here, ctrl s to save and then click on the terminal again press the upper arrow 79 00:05:31,890 --> 00:05:38,250 key to call a previously executed command and execute and you get hello 81 00:05:38,250 --> 00:05:43,740 and 7 and yeah this is how to use the Atom editor. Now this is good 83 00:05:43,740 --> 00:05:48,360 because you have both, you have the directory tree here with your files, with 85 00:05:48,360 --> 00:05:52,530 your Python files and you have the editor here and you also have an 87 00:05:52,530 --> 00:05:57,539 embedded terminal, so I hope you like Atom and from now on I'll be using 89 00:05:57,539 --> 00:06:03,680 Windows, but things will be exactly the same because Python is a cross-platform 91 00:06:03,680 --> 00:06:09,620 so which means the code is exactly the same on Mac, and Windows, and Linux as 93 00:06:09,620 --> 00:06:15,020 well so just follow me and I hope you succeed with Python. I'll talk to you 95 00:06:15,020 --> 00:06:17,169 in the next lecture.

External Links:~ https://www.windowscentral.com/how-add-open-command-prompt-window-here-back-context-menu-windows-10 Frequently Asked Questions: file:///C:/Users/Taha%20Umar%20Farooq/Videos/FOLDER/[Tutsgalaxy.com]%20-%20The%20Python%20Mega%20Course%20Build%2010%20Real%20World%20Applications/01%20Getting%20Started/009%20Installation%20FAQs.html 1 00:00:00,000 --> 00:00:05,190 Hey hello again in this lecture I'll show you how to download and install the 3 00:00:05,190 --> 00:00:11,309 Atom editor. Atom is a powerful and very efficient editor for writing and 5 00:00:11,309 --> 00:00:18,510 executing Python code. This lecture is specifically for windows, so for Mac 7 00:00:18,510 --> 00:00:24,869 users please go to the next lecture. So before what we did was we installed 9 00:00:24,869 --> 00:00:30,660 Python and we tried a python interactive session in the command prompt and we 11 00:00:30,660 --> 00:00:36,059 also created a python program using a simple editor such as Notepad or 13 00:00:36,059 --> 00:00:40,860 whatever editor you had in on your Windows, so now we're going to use 15 00:00:40,860 --> 00:00:45,570 another editor which is Atom and you need to go and install it from and 17 00:00:45,570 --> 00:00:54,480 download it from the Atom official web Page, just click the button there. 19 00:00:54,480 --> 00:01:01,800 Say file and it will take a while until it downloads. Great, the download process 21 00:01:01,800 --> 00:01:08,100 has finished now so I'm going to click on Atom, click on run to run 23 00:01:08,100 --> 00:01:16,380 the installation and yeah you have to wait a while until Atom is installed. 25 00:01:16,380 --> 00:01:23,189 And yeah, the installation was quick and now Atom has been opened on my Windows, however I would 27 00:01:23,189 --> 00:01:29,909 like to close it here and show you the standard way of how to open Atom, so the 29 00:01:29,909 --> 00:01:35,670 way that you'd normally open Atom when you start programming so one way to 31 00:01:35,670 --> 00:01:41,430 open Atom is to browse through your programs and open Atom by clicking. 33 00:01:41,430 --> 00:01:48,630 However that we open atom in a random directory so the most efficient way to 35 00:01:48,630 --> 00:01:53,790 open Atom is to go to the directory where you have your programs so the 37 00:01:53,790 --> 00:01:58,920 program that we have is myprogram.py. And then outside in here right click 39 00:01:58,920 --> 00:02:04,649 and go to open with Atom, but if you don't see open with Atom like I do. so 41 00:02:04,649 --> 00:02:09,250 I don't have open with Atom for now, then go and open Atom 43 00:02:09,250 --> 00:02:22,120 for your programs. Go to file, settings and then check these two options so this 45 00:02:22,120 --> 00:02:27,250 options were under system, under the system tab of the settings menu and I 47 00:02:27,250 --> 00:02:35,050 close Atom and I right click and now you should see this menu in here. Open it 49 00:02:35,050 --> 00:02:41,620 and you should now see this view but if you see, if you don't see the tree 51 00:02:41,620 --> 00:02:50,260 view in here, the directory tree view, go to view and then toggle tree view so you can 53 00:02:50,260 --> 00:02:59,950 toggle it off and on. You can close this and then to open your program, so to edit 55 00:02:59,950 --> 00:03:04,989 your program you simply double-click your file your Python file and yeah, you 57 00:03:04,989 --> 00:03:13,209 start writing. Print. Start adding more code and always press ctrl s to save and 59 00:03:13,209 --> 00:03:21,010 now to execute this code you can either go here and open your command window 61 00:03:21,010 --> 00:03:26,830 here with Shift right click or there is a more efficient way to do it. You need 63 00:03:26,830 --> 00:03:34,870 to go to file settings, packages, sorry install, you want to install a new 65 00:03:34,870 --> 00:03:48,610 package and search for that platformio 67 00:03:51,340 --> 00:03:58,299 click install and so this is the package that we will install or will integrate a 69 00:03:58,299 --> 00:04:04,510 terminal, a command line inside Atom so you don't have to use external windows 71 00:04:04,510 --> 00:04:10,180 and native windows command line and you can run your programs from within Atom. 73 00:04:10,180 --> 00:04:15,610 All right, platform ide terminal was installed successfully, you can close the 75 00:04:15,610 --> 00:04:22,510 settings tab and so now you should see this plus icon in here, click on the icon. 77 00:04:22,510 --> 00:04:26,870 Will open a new terminal so now this is 79 00:04:26,870 --> 00:04:32,030 opening the current directory which reflects the directory of your Atom 81 00:04:32,030 --> 00:04:37,400 directory, so of your programs. Now you can go ahead and type in commands you to 83 00:04:37,400 --> 00:04:43,880 run your Python program, so my tab for auto completion and that will 85 00:04:43,880 --> 00:04:48,260 auto complete like that, don't worry about this. This just means the current 87 00:04:48,260 --> 00:04:55,520 directory, so when you do Tab, Tab will add this. Ignore it and press Enter and 89 00:04:55,520 --> 00:05:02,690 you see the program output in the terminal. You can clear the terminal from 91 00:05:02,690 --> 00:05:07,970 the codes from previously executed commands and of course you can call 93 00:05:07,970 --> 00:05:13,730 previously executed commands with the upper arrow key. Execute again and don't 95 00:05:13,730 --> 00:05:21,380 confuse executing a program with opening a Python interactive session, so here you 97 00:05:21,380 --> 00:05:28,880 write Python code like print 7 for example interactively but if you exit 99 00:05:28,880 --> 00:05:36,229 this because I see some students will go ahead and run Python code in here but 101 00:05:36,229 --> 00:05:43,820 this is wrong, this is not Python, this is windows, the windows command line, so 103 00:05:43,820 --> 00:05:49,820 don't do that instead write Python code inside an interactive session or inside 105 00:05:49,820 --> 00:05:54,020 the Python file. That's the idea and this is Atom. I hope you like it 107 00:05:54,020 --> 00:05:57,160 and I'll talk to you later.

External Link:~ https://www.windowscentral.com/how-add-open-command-prompt-window-here-back-context-menu-windows-10 Frequently Asked Questions: file:///C:/Users/Taha%20Umar%20Farooq/Videos/FOLDER/[Tutsgalaxy.com]%20-%20The%20Python%20Mega%20Course%20Build%2010%20Real%20World%20Applications/01%20Getting%20Started/009%20Installation%20FAQs.html 1 00:00:00,000 --> 00:00:04,859 Hey welcome to this new lecture and in this lecture I'm going to show you how 3 00:00:04,859 --> 00:00:12,059 to create and execute a Python program on a Mac computer, so if you are a 5 00:00:12,059 --> 00:00:17,520 Windows user please skip this lecture. And so in the previous lecture I showed 7 00:00:17,520 --> 00:00:25,080 you how to install Python 3 and also how to launch a Python 3 interactive 9 00:00:25,080 --> 00:00:33,809 Session, so which is good for executing and testing out code so like that line. 11 00:00:33,809 --> 00:00:43,410 Like my line, but if you quit the terminal you're going to lose that code, so you 13 00:00:43,410 --> 00:00:49,800 want to find out a way to save that code in a file so that you can develop your 15 00:00:49,800 --> 00:00:56,010 program step by step, so you can go back to your code, add the code, modify it, and 17 00:00:56,010 --> 00:01:01,379 most importantly you can execute multiple lines at once instead of 19 00:01:01,379 --> 00:01:06,659 executing line by line interactively. So let's go ahead and do that. 21 00:01:06,659 --> 00:01:11,700 Normally you need to figure out, to create a directory where you want to 23 00:01:11,700 --> 00:01:17,850 save your program, so I'm going to create this folder in here and this is empty 25 00:01:17,850 --> 00:01:25,590 for now, so I'm going to create a file there. There may be different ways 27 00:01:25,590 --> 00:01:32,189 of creating a Python file all but I prefer to do it via the terminal. 29 00:01:32,189 --> 00:01:37,560 So currently you do PWD, that will print out the current directory of the terminal, 31 00:01:37,560 --> 00:01:43,049 so the terminal is an app and it is opened in the current directory, in a certain 33 00:01:43,049 --> 00:01:50,399 directory which is this on for the moment. If you do ls you will see the 35 00:01:50,399 --> 00:01:56,939 directories and files or the current Directory, so users admin has this 37 00:01:56,939 --> 00:02:03,090 directors, has these folders so if you want to go to the desktop folder, 39 00:02:03,090 --> 00:02:08,080 you'd want to do desktop or you can use the Tab for auto 41 00:02:08,080 --> 00:02:16,360 Completion, so the tab key and then Un Tab. That will take you to the 43 00:02:16,360 --> 00:02:24,250 untitled folder. Execute and I'll see that your current folder is the untitled 45 00:02:24,250 --> 00:02:32,020 folder and that means you can go ahead and create a file now. Let's say touch my 47 00:02:32,020 --> 00:02:42,070 program dot py, so you can give it any name that you want. Execute and that 49 00:02:42,070 --> 00:02:49,420 will create an empty file which for now you can go ahead and edit it with text 51 00:02:49,420 --> 00:02:54,160 edit for example. Later on we're going to install Atom editor which is much 53 00:02:54,160 --> 00:02:59,709 more advanced than this simple editor but for now this should be enough to 55 00:02:59,709 --> 00:03:06,580 just get you started to get you the idea on how to execute a Python program 57 00:03:06,580 --> 00:03:12,340 so let create code for the program. This program will simply 59 00:03:12,340 --> 00:03:20,230 print out the hello text so you need, you use this print keyword and then you use 61 00:03:20,230 --> 00:03:28,600 double quotes and then the text hello and then another double quote to close the 63 00:03:28,600 --> 00:03:32,760 text and then a closing bracket. 65 00:03:46,470 --> 00:03:56,520 CTRL S to save, exit text edit and then go back to the terminal and what you do 67 00:03:56,520 --> 00:04:00,930 here now to execute your program, the program that you just created, you use the 69 00:04:00,930 --> 00:04:07,200 Python 3 command and then my, you can type my program dot py or you can use 71 00:04:07,200 --> 00:04:14,760 tab to autocomplete the name, enter to execute and you get the output of the program. 73 00:04:14,760 --> 00:04:20,040 Print it out in the terminal so in this case the output is hello and yeah that's how 75 00:04:20,040 --> 00:04:24,570 you create and execute a program on Mac and similarly you can go ahead and 77 00:04:24,570 --> 00:04:31,050 create other Python programs in here just as we did with my program dot py. I can also 79 00:04:31,050 --> 00:04:35,730 show you a quick way to actually open the terminal in this current directory 81 00:04:35,730 --> 00:04:42,690 without having to do CD and try the path name, so let's do that. 83 00:04:42,690 --> 00:04:50,460 You go here, system preferences, so this is a one time configuration. Go to keyboard. 85 00:04:50,460 --> 00:05:03,150 Shortcuts and then in the shortcuts tab you go to services, scroll down and see 87 00:05:03,150 --> 00:05:08,070 you probably have this option unchecked, so you want to make sure you 89 00:05:08,070 --> 00:05:13,590 have checked the new terminal at folder option just like I have it here, so make 91 00:05:13,590 --> 00:05:20,490 sure make sure that is checked. Close this and then what you do is to open the 93 00:05:20,490 --> 00:05:25,350 terminal in a current folder, in a specific folder you right click on 95 00:05:25,350 --> 00:05:34,110 folder and then go to New Terminal at Folder and now what you do is Python 3 97 00:05:34,110 --> 00:05:39,390 Myprogram.py, execute and you get the Output, so that's a quick way to open 99 00:05:39,390 --> 00:05:44,100 the terminal in a specific folder and yeah that's about this lecture. 101 00:05:44,100 --> 00:05:50,210 I hope everything went smoothly and I'll talk to you later. Thanks.

External Link:~ https://www.windowscentral.com/how-add-open-command-prompt-window-here-back-context-menu-windows-10 Frequently Asked Questions: file:///C:/Users/Taha%20Umar%20Farooq/Videos/FOLDER/[Tutsgalaxy.com]%20-%20The%20Python%20Mega%20Course%20Build%2010%20Real%20World%20Applications/01%20Getting%20Started/009%20Installation%20FAQs.html 0 00:00.240 --> 00:08.010 H, again. In this video I'll show you how to create and how to run a Python program. In the previous lecture 1 00:08.060 --> 00:13.070 we set up Python and we ran a Python interactive session. 2 00:13.260 --> 00:15.960 So that was like a running code line by line. 3 00:16.170 --> 00:22.020 But what you want to do instead, we want to write code that we are able to save it in a file and we're 4 00:22.020 --> 00:25.150 able to run all the code at once. 5 00:25.200 --> 00:27.220 So that's what we're going to do in this lecture. 6 00:27.460 --> 00:30.720 And this is targeted to Windows users. 7 00:30.720 --> 00:32.940 So if you have a Windows computer please watch this. 8 00:32.970 --> 00:38.550 If you have a Mac computer or even a Linux computer please skip this video and go to the next video 9 00:39.240 --> 00:44.070 where I show you the same process but on a Mac computer. So Windows users, 10 00:44.220 --> 00:52.230 let's create a Python program and we're going to use very basic tools for now. 11 00:52.250 --> 00:59.760 But then in the next lecture we're going to download and use an advanced editor. On Windows before creating 12 00:59.760 --> 01:00.850 the program 13 01:00.890 --> 01:06.840 there is something you need to make sure of. You go to organize and you go to folder search options 14 01:07.590 --> 01:12.990 you go to View and then look here for this option. 15 01:12.990 --> 01:15.510 Hide extensions for known file types. 16 01:15.600 --> 01:23.380 You want to make sure this option is unchecked just as I have it here. Don't check it. 17 01:24.230 --> 01:34.170 Cancel that and with the option unchecked you go had and right click and create create a text document. 18 01:34.710 --> 01:36.180 And put a name. 19 01:36.180 --> 01:41.670 Let's say my program and you want to remove the txt extension. 20 01:42.120 --> 01:43.660 And want to say .py. 21 01:47.800 --> 01:48.290 OK. 22 01:48.320 --> 01:49.160 No problem. 23 01:49.190 --> 01:51.100 I want to change the name. 24 01:51.470 --> 01:54.970 Now this is a file where you're going to write your Python code. 25 01:55.070 --> 01:59.750 So just go ahead and edit, edit it with an editor that you have. 26 01:59.760 --> 02:02.760 Maybe Notepad. 27 02:02.900 --> 02:05.030 We're going to use Atom later. For now 28 02:05.030 --> 02:05.790 this is good. 29 02:06.070 --> 02:12.080 And this program, what this will do, it will print out some text. 30 02:12.320 --> 02:14.690 Let's say the 'Hello' text. 31 02:14.750 --> 02:20.300 So that's what you do, you use the Python print function, and the print function 32 02:20.300 --> 02:21.760 has this syntax. 33 02:22.070 --> 02:26.320 So it expects to have some brackets opening and closing brackets. 34 02:26.590 --> 02:31.690 And inside these brackets you want to pass the thing that you want to print out. 35 02:31.700 --> 02:36.020 In this case this is called a string. We'll cover strings later. 36 02:36.140 --> 02:38.520 Or you can say text. 37 02:38.660 --> 02:42.690 So we want to print out some text and text goes inside quotes always. 38 02:42.940 --> 02:53.930 So strings go, strings go inside quotes. Make sure you want to save control s, exit the script and then click 39 02:54.030 --> 03:01.610 outside in here and hold shift and then right click and then you want to go to 40 03:07.910 --> 03:12.330 Open command window here that you open the command prompt. 41 03:12.440 --> 03:16.560 Look carefully and you'll see that the command prompt was open. 42 03:16.560 --> 03:25.370 In this current directory which reflects which is actually the directory of your python file. 43 03:25.430 --> 03:28.960 So this one in here. This one in here is in here. 44 03:29.360 --> 03:36.050 So before you run the program you need to have these two directories the same because if you open 45 03:36.050 --> 03:44.250 the command prompt from here as we did in the previous lecture that will go to another default directory. 46 03:45.240 --> 03:48.870 So the best way to do it as I did it here. 47 03:48.990 --> 03:56.520 Click and go to open command window here and then what you do is you type python and then the name of your 48 03:56.520 --> 04:07.080 program, my program.py. So what you're doing is you're using Python, the python program to execute 49 04:07.200 --> 04:14.690 this file and you get the output in the command line which is hello, the text Hello. 50 04:15.960 --> 04:25.780 Similarly I could execute it with my Python 3.6, dot py and you get the same output again. 51 04:25.890 --> 04:29.180 So 3.6, 3.7 doesn't make any big difference. 52 04:29.190 --> 04:31.560 The differences are very very slight. 53 04:31.590 --> 04:33.670 So you don't have to worry about that. 54 04:33.690 --> 04:36.320 Let me execute it one more time, Python. 55 04:36.540 --> 04:44.480 If you type now my and if you press the Tab key, that will autocomplete the name of your file. 56 04:44.480 --> 04:50.130 So it will find the name of your file because it knows that you are in the current directory so use Tab 57 04:50.130 --> 04:54.670 for auto completion and yeah, again you execute it and you get the output. 58 04:54.930 --> 05:02.130 Of course you can go ahead and add other lines of code there. Let's say print 7, a number. 59 05:02.130 --> 05:10.710 Numbers don't go inside quotes, control s to save and close and go to the command line again and press 60 05:10.890 --> 05:15.780 the upper arrow key to execute, to call a previously executed statement. 61 05:15.840 --> 05:19.580 So upper arrow key will call Python my program.py. Execute and you get 62 05:19.590 --> 05:19.990 Hello 63 05:20.020 --> 05:22.120 and 7. That's the idea. 64 05:22.140 --> 05:24.890 Hope you enjoyed this and I'll talk to you in the next lecture.